One of the coolest features is the "peek." From any application, you can swipe your thumb up from the bottom of the screen, then right, to slide the application slightly off the screen. That reveals the messaging "Hub," which gathers your communications. At a glance, you can see which accounts have new messages. If you want, you can slide the app farther to the right, getting you into the Hub to read and write. Swipe left, and you're back to where you were.
The interface takes time to get used to, and it doesn't have the simple immediacy of the iPhone. But once you learn it, you can positively zip between tasks.
