I've never heard of Pixen, myself. The stuff I mentioned, is free, as I said. ArtRage you can download and use, but it has some features disabled unless you buy the full version. Photobie is good for making Animated GIFs, but the layers make me confused (which shows how much I need to learn about digital art), and Brush is really amazing considering how little/unknown it is.
You should ask Jill to put some stuff up, I'd like to see that.