My money is on UX. But let's hear it from OP.

While acengiano here is being downvoted, this is really one of my biggest gripes with Gimp. I'm having a terrible user experience.

It also doesn't help that I'm already well used to the paint.net/photoshop keyboard shortcuts. Besides Gimp having its own, different keyboard shortcuts, it also has some unique (and again different) conventions for how to use the mouse to select regions and stuff like that.

It may be equally productive once you're used to it, but I never liked Gimp enough to get into how the different ways it has chosen to do things actually works.

Gimp shortcuts aren't displayed, most often. Try creating a path and draw a line on it: You'll have to use the mouse very, very often. And you'll only find the shortcuts if you search online.

That's sad because you could be much more efficient with it.

GIMP is too complex (and too slow to startup) for simple image editing tasks.

None of the substitute photo viewer type apps on Linux really seem to stand in particularly well either - I like Shotwell at the moment, but it still lacks an easy to use crop/copy/paste workflow.

Are you aware of Darktable? I think it's a great Adobe Lightroom replacement, even has some features the latter is missing I believe.

http://www.darktable.org/

Wow, this looks awesome! I own and use Lightroom now, but will give Dark Table a look.

gThumb has been my favourite for years for quick resize/crop/rotate/white balance edits and image folder browsing. I don't know why it never was picked as default on Linux Desktops.

On this comment I checked it out and it looks like gthumb does a address a lot of problems. Thanks!

For me on Windows it is dog slow, even on i7 system.

Don't get it actually, as it a native code application coded mostly in C, unless Python and Guile plugins now own the majority of the code.