I have been using Photoshop for as long as I can remember. Since I am expecting my new laptop, I am on a search for opensource programs. Adobe Photoshop CS3 Extended costs $999 and there is no way that I would ever buy it. Thats when I found GIMP…
GIMP (GNU Image Manipulation Program) is the best free (opensource) alternative to commercial photo editors, like Adobe Photoshop. It allows you to do tasks like photo retouching, image composition and image authoring.
It features layers, channels, paths and other common painting tools and can do almost anything Photoshop can. The interface is slightly different than Photoshop, but it is very easy to get used to. However, be aware, it takes a bit of playing around to understand all there is that you can do.
You can see a few features of GIMP here.
So, if you are still using a pirated version of Photoshop, GIMP is definately worth a look. If you have a genuine copy of Photoshop I recommend you stick with it.
My hope is that GIMP will be able to rival photoshop one day.
If you want the photoshop feel on GIMP use Gimpshop, which is a mod of the original that brings the feel of photoshop to GIMP
http://plasticbugs.com/?page_id=294
I would rather go with Pixel – http://www.kanzelsberger.com