Note: This post is no longer being updated. There's a more comprehensive and up-to-date list available on Google at: iOS 4.0 Compatibility List Since it is now becoming possible to jailbreak iOS 4.0 GM, I thought it would be helpful to create a list of Cydia Apps which are compatible with the new OS. I will update the following list to reflect my own experience and your posts. Please note: I am only testing these on a 3GS; I don't know if there will be differences between models. Compatible AT&T Carrier Logo CallMe Cydelete Flashlight Lockscreen Clock Hide MakeItMine OpenSSH PDANet RedLaser (Cydia version) installed via .deb SBSettings 3.0.12-11 Beta (installed from BigBoss' Beta Repo) ToneFxs WiFi Sync Partly Compatible iFile (except web server) Haptic Pro Not Compatible: 3G Unrestrictor Backgrounder Cyntact (causes safe mode on start) Element Five Icon Dock GV Mobile iBlacklist InfiniDock (causes safe mode on start) InfiniBoard LockInfo Lock(Info) Weather Mobile Terminal (crashes to SB) Music Controls (settings panel will not load, cannot be invoked) MyWi OverBoard (crashes to safe mode) Popup Blocker Qik (Cydia version) installed via .deb Safari Download Manager Shrink Six Icon Dock StatusNotifier (crashes SB) WeatherIcon (crashes SB) Winterboard Looks like most things that use MobileSubstrate will not work.