I know many people have strong feelings about GIMP, and I just have to say that I love it. I use it for basic photo editing stuff—I’m not an artist—and it has always done what I needed it to do.

I gave up on comparing it to Photoshop over a decade ago, and by simply accepting it as its own thing (learning how it works and not grumbling about how this/that isn’t how Photoshop does it), it’s really not that difficult to learn. Just like vi (or photoshop) it’s a powerful tool and you need to spend some time to gain competence with it.