software - What are the key photography-related features from Photoshop that are missing in GIMP?

I am on a tight budget and chose to use GIMP for editing since it is free.

What important photographic post-processing features am I missing from Photoshop?

Answer

For photos? Not too much, actually. GIMP lacks automatic HDR processing. It doesn't have adjustment layers - although you don't need those too much for photos. Photoshop's Hue\Saturation dialog is superior. Photoshop CS5 has content-aware fill, which GIMP lacks, but there's a GIMP plugin called Resynth that does about the same thing:http://www.logarithmic.net/pfh/resynthesizer

Some pretty good art has been done in GIMP. (My snow photomanip, for instance) It's more about the artist's skill than the tools he\she uses.