I know this is a long post, but I spent about a week researching all of the apps listed on this thread and finally wound up downloading Things and OmniFocus (and heavily considered TaskPaper as well), and watched all of the related videos (including like 2 hours of OmniFocus tutorials). I just wanted to post some (somewhat) detailed feedback on what I discovered, since I see a lot of very simple posts such as, "I like 2Do", but with no real explanation or reasoning behind why the poster likes it or decided on it over all others. So, hopefully the time I've taken to find out all of this stuff for myself will help some others determine what is the best system for them.
First off, let me say that if you are looking for a "To-Do" list (or Task/Project Manager) app, but haven't yet read David Allen's "Getting Things Done", I highly recommend you don't purchase any To-Do apps (especially the pricey desktop versions of anything) until you read the book. The book will turn you on your head (at least it did me). Within the first 20 pages I was thinking to myself, "No wonder why I never get anything done, always feel so scatter-brained and stressed out, and continually forget things." His explanation / system will have you thinking, "Man, if only I'd found this process years ago." The way he explains things you'll think, "That makes perfect sense...why didn't I or somebody else figure this out years ago?"
Secondly, even though this thread originally started off asking about iPhone apps, I think that most Task Managers are most effective when you have both the app and the desktop version.
I'll start off with the one that I think is the simplest (not to be construed as "rudimentary" or "primitive"), then proceed up through the most all-encompassing.
TaskPaper is a very slick, clean and concise task manager that deals primarily with the basics....getting things out of your head and onto "Paper", with the ability to organize and rearrange those Projects and To-Do's with great ease. It has a very nice and clean GUI, slick functionality and some clever search ability. It's very minimalist (and I mean that in a good way). It sort of reminds me of those scenes in movies where somebody's kitchen or living room has very chic, well thought out, Feng Shui-ed
Poggenpohl furniture, and no extraneous anything, anywhere....everything there is crisp, clean, tidy and functional.
In watching the video, I didn't see that you could set Due Dates, Reminders or Repeat Events (that's not to say that the program definitely doesn't do those things, I just didn't see that showcased in the video). Since I'm borderline ADD and have a million things that I need to be constantly reminded of every day, I decided I needed something a little more robust and in my face (even though I love the slick, minimalist look with which Jesse has designed Task Paper).
Then I checked out
Things.
I like the way Things looks...very polished, bright, fun...ya know, Apple-y.
I really liked the interface and the fact that you could assign multiple Tags (i.e.: Contexts) to something (thus making your items very searchable). This was one thing that I liked about Things, more so than OmniFocus (mutiple tags / contexts for a single item or event).
For instance, say you really needed to go buy something at Macy's for your date this weekend (so it is a High priority). In Things, you could assign the tags: Macy's and Mall and High Priority....etc.,etc, as individual tags (and search by those tags in the "Intelligent Tag Search Bar" at the top of the screen). In OmniFocus, however, you create a breadcrumb trail (think of a breadcrumb trail as sequential, or like a folder within a folder within a folder....i.e.: the descriptors are all linked together in a chain and not individual descriptors). A context in OmniFocus might look something like this....Errands : Shopping : Mall : Macy's...which is in and of itself very specific and detailed, but because all of the descriptors (or "Tags" or "Contexts", whatever terminology you prefer to use) are linked to each other in OmniFocus, if you wanted to add the Context (or Tag) "High Priority" to that task, then you'd have to create an even more specific context for that event, such as High Priority : Errands : Shopping : Mall : Macy's.
So, in Things you can throw Tags at your tasks like darts at a dart board and they are all standalone Tags, whereas OmniFocus is more like that childhood game "Barrel of Monkeys" where all the monkeys have to hold hands.
The only downside I can see to the way Things does it is the "Intelligent Tag Search Bar"...if you have more than about 15 Tags, that top portion of the Things window is probably going to get pretty cluttered with Tag buttons.
Another things that I did like about Things and didn't see if it was doable in OmniFocus was the ability to drag any event you wanted to do Today onto a pre-programmed "Today" icon. In OmniFocus, you could always create a "Today" Project and drop your tasks into that project...or you could assign a Due Date of "Today" and then the task would appear in your "Due" context button in the OmniFocus desktop window, or in the "Due Soon" icon on the iPhone app...but I think Things' pre-programmed "Today" icon/folder is a better (read: simpler) way to keep you apprised of the things you want to do today.
While I really like the glossiness / Appley-ness of Things, there were a couple of reasons that prevented me from laying down my ducats for it.
First and foremost were the scathing, acerbic and venomous criticisms of Culture Code's customer service. Even my computer started to get a little heated up when it had to display some of the vitriolic (bordering on seething) feedback from disgruntled legacy customers. Apparently some of the features that Culture Code has been promising for quite some time, are nowhere to be seen, and the company apparently doesn't reply to emails from it's customers (I will say however that I sent them a question about the "Nearby" feature their competitor OmniFocus has and inquired if they were thinking about adding similar functionality, and they replied to my email within about 2 days...so maybe they've taken all of that criticism to heart and turned their customer service protocol around). Needless to say, however, I want to know that if I buy something, I definitely want to get the feeling that I can call / email the company that sold me the product, at any time, and have them get back to me. The fact that so many past customers lambasted the company for "taking my money and running" (to paraphrase a lot of people on various sites I researched), really didn't sit well with me. I think the one other feature, or lack thereof, the prevented me from buying Things was the fact that the iPhone app didn't have a "Nearby" function, which OmniFocus did (and I'll explain what that is in the OmniFocus section).
OmniFocus. Where to begin. OmniFocus allows you to do anything and everything with regards to categorizing, sorting, contexting, macro-managing, micro-managing any and all of your projects and to-do's. For most people (especially if they are just looking for a simple to-do list), OmniFocus will be overkill. We've all walked on board an airplane and looked in the cockpit at all of the buttons, dials, gauges and lights and thought to ourselves, "Holy crap!...look at all that...how do they keep that all straight?" OmniFocus is kind of the same way....it can be dialed in to the n-th degree and let you really get nitty gritty about how intricately you deal with your projects and to-do's. And yes, as others have said, it would behoove anyone thinking about going the OmniFocus route to spend 1-2 hours and watch the
OmniFocus for Mac and
OmniFocus for iPhone tutorials. Big Picture...OmniFocus is much more detailed, robust and well thought out than Things (albeit not as shiny and Apple-y). Aside from the constant software improvements, (reportedly) great customer service and incredible functionality of OmniFocus, the iPhone app sealed the deal. It too, is extremely detailed and well thought out. The thing I like best about the OmniFocus iPhone app is the "Nearby" function (something Thing's iPhone app lacked, as previously mentioned). What the "Nearby" function allows you to do is use the iPhone's location awareness (via it's GPS capabilities) to pinpoint where you are and what you can get done there.
When you assign a physical location as a Context (such as "Mall" or "Post Office"), you have the option to assign it an address or GPS coordinate. If you happen to be standing right in front of the Mall, you can tap on the Edit button for "Mall", then tap on the "Current Location" button, and the GPS in your iPhone will figure out the coordinates for where you are standing and assign that to the context "Mall"...and from then on, your phone will know the physical location of the Context you call "Mall". If you do this for all of your contexts that are actually places (Home, Work, School, Auto Mechanic, Grocery Store, Post Office, Aunt Sally's, etc.), then any time you hit the "Nearby" button, it will search all of your To-Do's, see if there are any contexts assigned to them (such as "Mall" or "Grocery Store"), see if those contexts have an address or GPS location associated with them, and then tell you how far your next nearest To-Do's are from where you are currently located. For instance, say I'm at my local Best Buy picking up something I need. Since this is in a shopping district that's some distance from my house, I should probably do all of my shopping while I'm there, right? But, I can't remember if there is anything around there that I also need to do while I'm in that area. We've all gotten home and remembered that there was that store we needed to go to (and forgot), and then get mad at ourselves because "I was just there." If I'm at Best Buy and hit the "Nearby" button, it'll remind me that Target is in the next parking lot and I have to pick up Thank You cards...that Macy's is less than 1 mile away and I need to pick up that outfit for my date this weekend...that the grocery store (near my house) is 8 miles away and I need XYZ...that my cousin, whom I'm going to see in Seattle in 2 weeks is 732 miles away....and so on. By having the "Nearby" function as part of the OmniFocus for iPhone app, wherever I am, I can become the epicenter of tasks nearby me, and get a lot more done.
The iPhone app will also let you do a search by Business Type if you have a To-Do, but aren't sure where to fulfill it. Say, for instance, one of your To-Do's is to buy flowers for your Mom before you arrive at her new house (in an area you are not familiar with). Well, something happens that day and you're running behind and you didn't have time to pick up flowers near your house before you got to Mom's new neighborhood. You can do a search for "Florist" and it will look through local business directories for the nearest florist so that you can go get the flowers before you arrive at Mom's.
Lastly, OmniFocus syncs Over the Air (read: Wi-Fi), through the Cloud, MobileMe, you name it...which I really like.
So, the net-net is, I chose OmniFocus because I love the "Nearby" functionality of the iPhone app (among other things), and would rather have a desktop Task Manager that has a few more bells and whistles than I need (or will use), rather than be stuck with a less robust desktop app and be pining for things it can't do.
Hope this helps.
Justin
P.S. One last To-Do application that I like the premise of, but it doesn't quite work as well for me, is
Life Balance. Life Balance is a little bit different than every other To-Do manager I've come across. It let's you set the priorities of your tasks, then when you check them off as done, you can look at a pie chart of the various areas of your life (Work, School, Father, Coach, etc.) and see a graphical (read: pie chart) diagram of how you're spending your life (both how you'd like to spend it, and how you are actually spending it)...then you can readjust the size of the pie slices to give more precedence to the things that you value, but that you aren't getting done...and Life Balance will re-prioritize your To-Do's to bring your actions more in line with how you want to spend your time.