Android Ice Cream Sandwich (ICS) on the Galaxy S II is nice, but I'm experiencing a few problems with lag, apps and phone hanging for no apparent reason. Wifi performance seems worse too. Since the ICS update, the wifi keeps dropping out on me in my office, which didn't happen before. My office doesn't get great wifi signal to begin with, but it's like ICS isn't as tolerant of low signal strength anymore.
I've already done a hard reset thinking maybe that would help. It's also possible that the problem is with the apps that maybe haven't quite caught up with code changes in ICS. Who knows.
Also, a somewhat subjective thing, but it seems like the graphics look better in ICS.
Will probably have more comments later as I use ICS more.