They are mind numbing because the GIMP UI is terrible. That's what happens when open source developers have control over UI vs. a marketing team that actually wants money for the product.

I use Paint.NET on my laptop as a nice paint replacement. It's does about 1/1000th the things that PS does. It is a good MS Paint replacement, not a good Photoshop replacement. I'd go with Paint Shop Pro before I went for Paint.NET for photography.