Its April and the next major iPhone OS release is here. iPhone OS 4. So whats new? There are over 100 new features, but here are 7 major features that were demoed at the event: 1. Multitasking. Apple has finally added multi-tasking to the iPhone. Its an essential feature when you have apps for music streaming and instant messaging. Now you can double tap the home screen to multi-task! Note: This only works on the iPhone 3GS and 3rd gen iPod touch. 2. Folders. With more apps, comes more icon space. Apple has introduced folders to add multiple app icons to. Just drag an app icon on top of the other to make them in a folder. Pretty nice implementation! 3. Enhanced Mail Application. Mails displayed together from all mailboxes and threaded grouping of mail (like Gmail). Nice enhancement. 4. iBooks. Apple's own eBook application is now on the iPhone so they can get over some Kindle book sales. Nothing major about this feature. Not exactly a feature, I would call it a new iPhone app by Ap