Re: Forget the geeky stuff, sort out the user experience.
I use gimp a LOT. The only mildly irritating thing is that I have to 'export' to any format other than the 'gimp' format. But that's ok, once I understood the semantics of their menu, no big deal.
And I'm glad there's AN ACTUAL MENU and NO [profanity spew] RIBBON nor FAT-FINGER-BURGER. Well, in the versions I've been running on FreeBSD, anyway... (2.8.18 and 2.8.22, which work pretty well)
One thing gimp does lack is some of the things that MS Paint has always had, some of its line and curve generators and related things. Maybe if I worked with it some more I could figure out how to work around that...