I disagree with you on the fast part, it is pretty quick. I'll check out SUMO now.. *MODIFY* @Chem : It's just like Photoshop, it,s free, it's online and doesn't take up much of your computer space.
There are plugins that make Paint.NET exactly like photoshop. I figured out howto use both simply, but I learned more through using Paint.NET The only thing that I don't like about PDN is that it can't animate.