I'm in the same boat as you, I need a good projects app but don't like what I see so far. I have Things, but its quite limited and just a To-Do list in my opinion, the notes apps are ok but I want something that does it all. I use Evernote a lot as that works great, but its for notes, not a To-Do list or project planner.
Basecamp is good, they do a free plan but you get no file sharing options and only 1 project with it, though your project can be as big as you like! Also the iPhone apps that work with basecamp don't allow file sharing of any sort as basecamp haven't enabled that feature in their API. I'm thinking of buying Outpost as that looks like the most promising app to work with Basecamp.
There is an app called Pocket Informant being shown at MacWorld, thats meant to be good, not sure if it will do what I need though!
If you find the perfect app do let me know, in the meantime I think a combination of Basecamp/Outpost and Evernote is the best way for me to keep organised.