The update gives us a ton of new features including built in Twitter Support for people who love to share. Also front and center is Notification Center, iMessage, Newsstand, Reminders and iCloud support.
The main thing at Good e-Reader we are concerned about is the new Newsstand application that allows customers to visit a dedicated app on your home screen and purchase magazines and newspapers! This is a great effort to condense all of this content in one place. It also has a dedicated section in the iTunes store now to purchase more content.
If you want an entire walkthrough of all of the new features check out TIPB.