Has anyone ran GIMP 2.0 long enough to compare them? whats the difference, which is better? (avoid the price conern) I am doing a retropsective for a proposal on linux in schools.

Also, I know that PS CS requires extensive processing power, how does that go for GIMP?

The Gimp, Photoshop, and any other image editing/manipulation application, including CAD, will be a resource hog. The more RAM you have, the better. You will also need plenty of reserve space on the hard disk to store the images. Which is better? Like any other app, it's what you get used to, or like best; any individual preference. I'm not a pro with either one. I've taken Photoshop in night school, and used Gimp at home. For what I've tried to do, they are equal. The terminology they use is a bit different one from the other. But, by keeping help files open and handy, I can equate what I did in school on Photoshop, to the Gimp equivalent, and do what I want to do, with equally impressive results.
My opinion, for what it's worth.

I don't know anything about CS, but used Photoshop daily from v4 to v7. Because of my experiences with PS I'm still a bit biased toward it. The Gimp has been evolving rapidly, though...faster than photoshop in my opinion, and will soon be at least as good if not better.
There are still a few things troubling me about the Gimp, the most prominent being that it falls short with resizing and optimizing images when compared to Photoshop. PS, since version 5.5, has had the "save for web" feature, which does an excellent job of compressing jpg, gif, and png...Gimp is decent in this area, but does not reach the same quality. Resizing, particularly scaling down, seems to be difficult for Gimpy...it's not noticable so much with photographs, but if you have an image with a combination of photo and fine lines, you'll see the lines quickly blur or disappear on resize.
Other than this, I'm very impressed with Gimp...particularly v2. If Gimp were a $700 program like PS, I'd stay with Adobe...but even if Gimp had a pricetag of a hundred dollars or so it would be a better investment than PS. As a free application, there's no comparison. It's truly an amazing tool.

I myself used to love using Photoshop, and the only thing that the GIMP doesn't have that Photoshop does are the layer attributes. However, it makes up for them with a much better text tool (keeps the text info, even when discarded) and a load of filters and script-fu actions.

Personally, I think that the GIMP beats Photoshop already. Perhaps it is because I haven't noticed the problems that some people are talking about with it, but right now I think that it's better than Photoshop. The price of the GIMP (free), easily beats the price of Photoshop. The GIMP is still in the early stages, and Photoshop's already at version 8.0, which shows that we've seen hardly any of what the GIMP is evolving much faster and that in the near future, I think that all the small problems people are talking about [most of which I don't notice], will be gone.