This is the number 1 thing that kills me and one of the main reasons why I wont switch.
iMessage is like the drug I never had before. The ability for client texts to go directly to my iMac or Macbook has become crucial for me (Majority have iPhones). I keep thinking to myself of getting a iPad mini with cellular and try voip just so I can have a bigger screen that my older eyes can see better.
I also like the iCloud syncing. I use a lot of notes and even though I have Evernote premium there are some convient quick notes I like taking in the basic note app that works well.
Hopefully Apple will come out with a 4.8 inch or greater phone. I rather not switch and the extra length in the iPhone 5 really does not make much of a difference for me.
The unreliable performance of iMessage on my macs is one of the reasons I was able to let it go. For a company that used to claim "it just works" there is no excuse for suddenly wiping out the last day of iMessage history when I am on my mac. More than once I replied to someone, thinking it was the last message, when in fact it was from much earlier. Then, all of a sudden, iMessage would re-sync and there was the correct history (not always in the correct order if I had replied when the message history was truncated). I often had to check my iPhone just to be sure the last messages I was seeing on my mac were correct.
The other thing that bothered me was the co-mingling of text and iMessage. It should be an advantage. But not when most people don't understand how it works. I had to explain soooooo many times why iMessage messages suddenly "turned green" or why they were delayed. iMessage will wait approximately 10 minutes before reverting to SMS. Well, unless you happen to know that if you tap on a message before it is sent you can force it to SMS right away (number of friends and family that knew that, before I told them: 0).
Which leads me to something that has bothered me about the iPhone/iOS since day one (I bought the original iPhone at launch): it will switch to a saved wifi network that either has no internet access or requires a login (such as an airport or hotel) when there is a perfectly good mobile data internet connection available. Essentially it is blindly killing your internet connection when it does that. Happened to me all the time and this is when iMessage would of course not be able to send a message until I either fixed the wifi issue or enough time went by that it reverted to SMS. When I switched from an iPhone to Nexus for this past November, and saw that it had the ability to not use wifi networks unless they had internet access I was thrilled. It was one of many "why can't iOS do that???" moments.
As for notes, there are countless apps on Android that do that and also sync--even to iCloud if desired.
Finally, I have apps on my Note 2 like MightyText and AirDroid that allow me to send and receive texts from any browser (PC or mac--or even my iPad should I want to).
Michael