My wife got the ICS push last night.
Issue #1 - The first issue was the system froze at updating applications. Let it run for ~30 minutes at this screen and the phone became VERY hot. Forced it down and when it came back up everything appeared OK. Battery took a 1/4 charge hit by doing the update. I've read quite a few forums where people had the same issue. This is more of an added FYI than anything.
Issue #2 - Facebook stopped working (force close)
Issue #3 - Both Gmail and Exchange email stopped working (force close)
Phone was rebooted a couple times, tried updating Facebook via the store, wiping cache etc etc. Nothing fixed it. We went to bed. This morning both issues (2&3) were "magically" resolved???!!
Facebook and both email accounts when accessed popped up asking for credentials. Credentials re-entered and viola???? Really? So odd to say the least.