GIMP is complete and utter garbage.
I installed it several months ago because I had to replace the HDD on my iMac. The version I had of Creative Suite was old and only an upgrade to an even older version I no longer have. So I was stuck.
So I decided to try GIMP. I used it years ago and didn't like it, but I figured it had improved in the intervening years. It clearly hasn't. I can't express enough how awful it is. First of all, it's outrageous that I have to hunt around to find an acceptable built. And even the recommended version is poor.
A lot of the problems are a total failure in UI design. The tool panel gets buried under images. Settings aren't retained, so every time I save a JPG, for example, I have to readjust compression settings. Select a tool and after using it on the first image it automatically starts trying to apply it when you select anywhere on subsequent images. The JPG compression algorithm is awful, producing excessive noise with minimal compression. Many functions are unintuitive, not consistent and cumbersome. Functionality breaks constantly. I'm not going to even get into the travesty that is the type tool.
GIMP is a nightmare to use in every single way. I'm constantly fighting the application. It feels like developers made a checklist of all the functionality in Photoshop and tried to replicate it all any way they could. So you get this inconsistent mishmash because no one tried to think holistically. And worst of all, it runs worse than Photoshop every did.
GIMP is a sad, miserable case for open source.