Update: Download iOS 4.1 final here
All iOS 4 jailbreakers should stay away from the iOS 4.1 update. iOS 4.1 beta is expected to have some enhancements to already feature-rich iOS 4.0 including the GameCenter which mysteriously went missing in the finlal release of iOS 4.0 Download iOS 4.1 beta [developer only] Update: Download iOS 4.1 final here