Apple has managed to fulfill yet another promise as it has rolled out the highly awaited iOS 4, formerly known as iPhone OS 4 or iPhone 4.0. You have every right to jump around in excitement since the latest iPhone firmware brings sensational features such as multi-tasking, folders and the list goes on.

iOS 4 which has more than 100 features and 1500 APIs is available for iPhone 3GS, iPhone 3G, iPod Touch 3G and iPod Touch 2G users. Users of iPhone 3GS and iPod Touch 3G will be getting the complete package of iOS 4 whereas the iPod Touch 2G and iPhone 3G users won’t be getting the multi-tasking feature among other missing features. The installation guide can be found here.

Update 1: Ultrasn0w 0.93 has been released, which brings unlock for iOS 4 and all other basebands since iPhone 3.0. Details here.