The software centerpiece of Apple's fall event today was iOS 4.1, available for free download next week. The new version of the OS delivers the expected fixes for problems with Bluetooth and the proximity sensor, along with speeding up performance on iPhone 3G (finally!). It also packs two major new features: Game Center and HDR photos.

Game Center allows you to compete against your friends in any compatible game, unlocking achievements and moving up the leaderboard. It also introduces the possibility of live player vs. player games on the iPhone, with Push-powered notifications when someone challenges you. You can add friends or let Apple match you up with opponents. Existing popular games will be compatible with Game Center, too: Steve Jobs showed a screenshot of a leaderboard for the bestselling Angry Birds.