BOOM widget 139340'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.