'Game Center' is one of the many features included in the update, enabling multiplayer gaming, game-based achievements, and leader-boards.
Also chief amongst the updates included in iOS 4.1 are iTunes TV show rentals (for $0.99 a pop), iTunes Ping (a Facebook-like notification feature for iTunes), HDR photography, and HD video upload capability. Check out the image for a list of additional feature updates.
Grabbing the update is easy. Just open iTunes with your iPhone connected and the update should take place automatically.
Given the close similarity to the name of Gamefly's app, has there been any discussion of rebranding it?