Since updating to ICS early this morning, I've noticed a couple of issues that I haven't found in the forums yet.
I added a Group to many of my contacts. Afterwards, found that on a few of them, when clicked in the Group tab, they would bring up a different contact. In each case the contact brought up was the next alphabetically in the overall list of people. Only seemed to be an issue in the Groups tab and not in the People tab. Fixed my removing and re-adding the bad contacts.
Also, had an app in the app drawer that I didn't recall downloading and when I went to uninstall, a different app was displayed in the confirmation dialog. Went ahead and uninstalled anyway and it appears the correct app was removed.
These both seem similar, as if an index was corrupted. Not sure if anyone has seen these issues as well. Otherwise, quite happy with ICS.