I got to play a little with Painter 6 a while ago, and was positively horrified by the awful interface. I absolutely loved the idea behind the program, but the program itself seemed pretty much unusable.

Just recently, someone dropped Painter 7 in my lap, and I though what the heck, it's not like I've got anything better to do... With a little experimentation, I have come to love "Color Variability" -- I do not have a tablet (yet), only a mouse, but CV is a great help for getting a more natural look. So far I'm thinking it must be a great tool for painting a base when making skin textures.

I don't think I will ever stop hating the interface, though.