This app is unabashedly my vote for the best iOS-6-to-iOS-7 redesign I’ve seen. It retains the spirit and flavor of the previous version, while still treading safely within the new flatness dictated by iOS 7. Get it here.
Playful animations are easy to spot but not overbearing, which is difficult to achieve. My favorite animation is the animating hearts when tapping a like button (I sure hope people don’t get push notifications every time I tap a heart button, because I can’t keep myself from tapping them again and again).
If I could change one thing, it would be the use of the blurring views behind the status and navigation bars. They’re so heavily tinted blue that the resulting effect is a distracting flicker when scrolling. The true purpose of iOS 7’s blur is to create the illusion that your “content” is always visible, even from behind a navbar. This goal would be better achieved in Tumblr’s case by using semi-translucent non-blurring blue bars.