Comment gimp vs photoshop (Score 1) 724
Firstly 99% of people probably don't need photoshop CS, and gimp is much more suited to them than photoshop CS is anyway. Gimp (version 2 and above at least) is easier to use and much cheaper than photoshop CS. This 99% of people is the photoshop elements market, and gimp beats photoshop elements hands down on most things (mainly because it has a `levels tool' [don't know if this has been added to elements 3]). Elements just has too many things missing.
For the other 1% of people, gimp does just not cut it. My main reasons for using photoshop are that it handles 16-bit per channel colour, colour calibration is easier and the workflow from the in-built file browser (which browses raw format files) through editing to printing is much smoother than with gimp. Gimp does do this at a push, but it is a struggle. Also adjustment layers are a dream (I don't know if these have been added to gimp recently).
As I said before, most people don't need these features, but most Pros probably do.
To finish, one place where gimp wins is on the channel mixer, where it is possible to lock the overall brightness level as you mix to monochrome.
Photoshop CS is currently missing this feature.