This seemed to me like a fairly minor upgrade in terms of usable functionality. I did have one or two minor issues with it. The most annoying one was folders - when you open a folder it says folder open. Close it, it says folder closed. No, it's not the accessibility settings - I changed all the settings I could find and none fixed it. What DID fix it was uninstalling light flow, which sucks since I love light flow. I got around THAT by installing Holo Launcher HD and used IT'S folders - JB doesn't whinge at me about them, so that's cool. I also installed Holo Locker, and now I have the cool lock screen rather than the lame Samsung one. It's possible the problem was there on 4.0, but I was using Apex Launcher and it's folders there. Carping - Why after this many iterations of Android don't we have the option to create a denser screen grid and dock? I shouldn't have to download an add-on to get that.
Also, coming off Blackberry the notification system seems woefully primitive, buggy and clunky. Come on, Android. Get with it. I truly cannot wait for the new BB10 handset. Some features of this phone make me want to go back to my 9930. Even now, no one handles messaging - SMS, MMS and email - anywhere near as well as Blackberry. If that was all I wanted to do, I'd go back to BB in a heartbeat.
My ideal phone - messaging and alerts from BB. Add the BB keyboard and the pure class of the 9930. Scientific and file sharing apps from iOS. Customization from Android. NOW we have something. Please oh great god of handsets - breathe new life into RIM. They are ideally positioned to create this phone for me - a great new OS, that BB heritage, the knowledge gained from watching where other systems are falling short, and a clean slate.
I tried to use the backup assistant thing, but it just sat there telling me it was uploading pics and stuff, and never, ever said it was done. Turns out it was lying about backing up and I lost them all off the phone. Fortunately I had copied them to my computer before starting.
I did not have battery discharge rate issues. Battery life seems about the same. An uneventful upgrade that I could have easily blown off and never missed. If you are happy with 4.0, don't be in a rush, or even don't bother at all. You won't suddenly be in Android heaven with this update - you will just be in a very slightly different neighborhood of the old home town, where you will meet everyone you already know.