Like its Android counterpart, the app does now have full tablet support, and looks great. But, unlike Android, the iPad version of Tumblr has a new radial menu for quick access to key functions. It's quite a bit like the UI you'd find in Path, if you've ever used that app. The radial menu has easy access to functions when you're composing a post, like adding a photo, video, link, etc.
If you want to give the app a shot, just head over to the iTunes App Store and grab it for free.