paint.net is awesome. But I like gimp more.
There's more stuff you can do with it, I like the layout in paint.net too.
But if you customize the gimp layout and shortcut keys it's very simple.
GG is quite crappy for what they give you with free and pay version...But I guess it's alright.
P.net is alot more to install with less plugins. But gimp is less top install with more plugins. Well, that's what it seems to me anyway. But p.net took a very long time to install, photo shop was faster at installing. (Same with GIMP)