I remember when I first downloaded the first official Tumblr app. It was clunky, slow, and didn't show what I wanted it to. I promptly gave up on it. Version 2.0, on the other hand, is actually something I'd use.
Bad luck if you're a fast-paced Tumblr fiend running anything less than Android 2.1 on your Android. Their first official Android app has no place on your phone.