DON'T -> Samsung Galaxy S2 Android 4.0 Update
For the five or so months that I have had my phone I have not had a problem. But I listened to all the buzz about ICS and had to have it. The upgrade went fine, but since then the phone crashes periodically, or just locks up. I am NOT a heavy user with a lot of downloaded apps and widgets. I listen to music and use the phone, and occasionally browse the web.
If anyone knows how I can go back please let me know. Unless there is something you really need in the latest release I wouldn't do it.