After a fairly quick update, Game Center will grace your iDevice with it's oddly implemented presence. Why oddly, you ask? Because there's not much that's compatible with it right now, I answer.
I actually have a lot of titles on my phone (shock D:) but only the original Pac Man works with GC. It's not even Championship Edition for God's sake!
After a very brief play of ol' Paccy, I had a few achievements. Yes achievements, I know it's shameless. Collecting 'cheevos on the iPhone is just as strangely satisfying as it is on the Xbox though, I just wish Apple had made sure there were more games that offered them before they launched.
Edit: I just saw that Real Racing by Firemint works too.