When iOS 5 was demoed at WWDC it was said to be having 200 features or so. In every beta of iOS 5 a new feature is added or enabled. Till now Apple has released iOS 5 Beta 4 for Developers and many new features are ported into it. Many new features were spotted in iOS 5 Beta 4 and rest are to come in the future releases. One of the new feature which was seen by me was hotmail Integration in the Mail.app.
If you have seen the previous iOS only G-Mail and Yahoo users had the advantage of using the Mail.app in their iPhone,iPod, or iPad. If their was some Hotmail user, so he had to either go to Appstore Apps or add the account by going into Other and add his account their.