The Incredimail app for iPad has a great-looking interface for browsing e-mail.
The visual inbox
With the Incredimail inbox, you get more info about messages with the limited number of messages on the page. You also can touch a message pane and swipe up to see a preview or swipe down to access controls for deleting, forwarding, and other actions.
An added bonus is the Facebook photo inbox that shows you the latest photos to be submitted to your Facebook feed. You can only "like" a photo (no comments), but the problem is that the app requires that you let it post on your behalf to your Facebook timeline.