Esoteric Software recently added Unity support to Spine, a new skeletal animation program I backed on kickstarter. If you are developing a 2d game I’d recommend checking Spine out! It supports quite a few game engines besides Unity, including Corona, Cocos2d, XNA, amongst others. Good UI and I haven’t had any stability issues.
The performance is great on my oldest test device (4th Gen iPod). Zero allocations if you aren’t swapping images, and very minor (less than 100 bytes) if you are, according to Unity’s profiler. So no worries about garbage collection! Here are some creatures I’m working on in Spine.