It's a great little free bit of software, very pretty, and also quite easy to use once you get the hang of one or two little tricks.
I did manage to crash it a couple of times, mainly when I tried to use Transform on a selection rather than a layer, but otherwise it's stable enough.
There are a couple of serious omissions though. Although you get Exposure, and Hue/Saturation, you don't get Levels, or Colour Balance, both of which I think absolutely essential in any layer-based image editor.
But, for a free app, it's neat. Just make sure you download the 0.5 Beta, not 0.1 which has far less in it.