I use it, but not really for image editing to be honest.. I use Aperture for that. I didn't want to buy Photoshop as I don't have a need for it and find it too expensive, and Aperture does all the photo editing I really need, so I bought Pixelmator, for small stuff like when I want to add a border or make some kind of diptych or a banner or whatever, or make some adjustments to a drawing, scanned or made on the iPad. It works fine for these purposes. I honestly have never tried editing a photo in other ways, is it any good for that? 🙂
Anyway, enjoy, it really is cheap, and thankfully not too complicated to understand, and, a big plus, Apple native. I hated Gimp because it didn't really work for me on an apple. Not that intuïtive. (and ugly.. :S )