Tumblr’s iPhone app just had a major update (see: Tumblr for iPhone 2.0: New Look, Features & Enhancements). However, it is not a “universal” iOS app that rescales for the iPad. iPad users should not feel negelected, however, because Tumblr tweaked their website to identify and optimize the way it works when you visit your Tumblr Dashboard.
I tried the new optimized web view by pointing my iPad’s Safari mobile browser at my personal tumblog dashboard. True to their word, my Tumblr Dashboard rescaled appropriately for both landscape (wide) and portrait (tall) views. Most of the buttons and menus worked as expected. However, you cannot upload media (audio, photos, video) directly from the iPad. Tumblr’s iPhone app lets you perform these actions. You can, however, use URLs (web addresses) to point to media already present elsewhere on the web.
The Tumblr iPhone app provides much better media tumblog item creation. However, the improved iPad webview should be very welcome by active Tumblr users (like me).