I've been using GIMP since pre-2.0 versions, when it was quite buggy (on Windows) and features were poor. With 2.2, frankly you can do most of the things you need other than colour management and CMYK separation.
Brush management is poorer than PS (I'm always impressed when I see a PS user scaling a brush like magic..) but the next release has reasonable brush scaling (2.3.xx development versions, which are currently quite stable on Windows). The most popular raw plugin, UFRaw, is very good, and has improved dramatically over the past months. It now includes an excellent denoiser, and it's interpolation routines are state of the art.
I'm not willing to pay for PS, in part because I'm proficient enough with GIMP that I can do all that I need. At $0, I can run one (legal) copy per PC/laptop at home and work.
I have switched to PS Elements 5.0. I think it's good enough for me. I could do things much faster than with GIMP.