iOS 5 Notifications
I really like that Apple has changed the notification model. It kinda/sorta works in this first beta. Facebook and Twitter seem to be real slow in even native notifications, which may be part of the problem. I have seen mail on the unified list a few times.
I wish the iPad had built in weather and stocks apps like the smaller iPhone/iPod, as that would be really handy.
Hopefully there will be abundant updates from third party vendors that will enable visibility in the new unified app.