Hey any that installed 4.1 gm where did your gamecenter icon end up? Mine is on the right of the settings button but if you watch the recent keynote it's on the left of the settings button. No big deal but I wonder why the difference ?
Mine ended up to the right side, but I moved it to the left and problem was solved.
if you restore your phone (not from a back-up), it will end up on the left to the settings app, so their is something in the upgrade path that causes it to not end up where it should.