Macworld posted a little first look-style preview of Snapseed earlier today. It at least gives some insight into how the program works.
http://www.macworld.com/article/160455/2011/06/snapseed_cool.html
I bought it because I've looked closely at Nik Software's offerings for several years, and I've liked what I've used of them, but I haven't been able to convince myself to buy the entire collection. A chance to play with a simplified version of their technology for $5 on the iPad seemed like a reasonable value.
So far, I really like Snapseed. I've got 2 other image-editing/drawing/filter programs on my iPad (FX Photo Studio HD and ArtStudio), and I think that Snapseed, for me, has been the most intuitive so far. The Macworld preview describes Snapseed as one of the most touch-friendly photo programs out there, and I agree with that. I don't think it's as flexible or powerful as the other two programs I have, and it's a little more expensive ($4.99 vs. $2.99), but, so far, it seems more intuitive for how I work. But I'll readily admit I've only played with it for a little bit, and I'm certain I've only scratched the surface of what it's capable of.