If you haven’t recently refreshed Cydia sources. iPhone developer Ryan Petrich updated Activator today to version 1.40-BETA 2. Two days ago Activator was updated to version 1.40-BETA 1, adding support for iOS 4.
No official changelog included, but Ryan mentioned on Twitter that most of iOS 4 bugs should be fixed.
Note: This is a BETA and Ryan would appreciate feedback from users on iOS 4.
Activator is available in Cydia via BigBoss repository. For the latest BETA version of Activator, add repository: http://rpetri.ch/repo