When gamecenter showed up, it was pretty awesome. But the thing is before, idk about now, gamecenter freezes you for a bit to send your scores to update gamecenter stats then updates it to the leaderboards. When you pk, spar or kill a baddy and you have gamecenter on, it freezes/slows you down at some point to update your stats. And also idk for anyone else but even if i turn off gamecenter it would always sign me in anyway and even if i turn off to update/sync score it still freezes/slows me randomly. So yeah, it got pretty annoying.