So I, like everyone else in this great country of ours, downloaded 4.1 today. For some, including owners of the previously thought dead 2nd gen iPod Touch, the 2 hour download couldn't come fast enough, but for owners of the iPhone 3G, there is no GameCenter. Sorry iPhone 3G owners.
After going through the setup process, I was greeted with the green gym-like screen that we all had seen only in screenshots. The obvious next step was to click on the "Games" tab and download some games, but alas, the link just sends you to apple.com/game-center, a site with no games listed. Discouraged, I set up my status as "Waiting for games", and then went on my merry way taking pictures with the new HDR feature. It turns out that the only game available was Ms. PAC-MAN, and anyone who has played Ms. PAC-MAN on the iPhone before knows that it... has its quirks.
Fortunately, since then a few notable games have added support, such as Real Racing, Flight Control, and Fieldrunners, so get playing! My Game Center SN is chris148apps, and I expect to have 10,000 friends by midnight.