The interface may be a little weird (or it used to be), but it's really powerful when you get into it. Sure, being effective in GIMP requires you to learn a few keyboard shortcuts but what software doesn't?
I was completely blown away once when I saw a hacker/artist friend of mine do some amazing artwork with GIMP (this was circa 2001). One hand on the keyboard, one hand on the mouse/wacom tablet. Sure, he was a hacker, so the interface may be a little more intuitive from that background but the artwork he produced spoke for itself.
I don't listen to pro-photoshop people's arguments any more. The interface may seem weird but it gets the job done. The 8bpp color was a major stumbling block but now it's gone. As are many other sources of complaints about GIMP.
You (and everyone) should really give GIMP another go, the improvement has been HUGE in the last 10 years. This is what a lot of people don't get about open source software. It improves constantly, if you did not like it 10/5/1 years ago, the chances are it's been improved during that time. And if you feel that something needs a change, you have the option of doing it yourself or helping the community put it together by whatever means you have to contribute.
Or just shut up and pay the license for Photoshop, but please don't come bashing people who are doing hard work to make GIMP/Blender/Inkscape better.