GIMP is certainly no Photoshop, but it does work very well for free.
I agree that it lacks tools Photoshop has, but Photoshop is so
incredibly powerful that many people will not use it to anywhere
near its potential.
Aside from the lack of proper CMYK support, the biggest complaint
with GIMP that I’ve heard is with the UI. My feeling isn’t that the
UI is bad, it’s just significantly different from Photoshop, and
having learned to use Photoshop prior to GIMP, I had similar feeling.
Now after some having used GIMP for some time, I feel quite
comfortable with it. Apparently the UI design is specifically
designed not to look like photoshop, however there is a program that
I’ve never used called GIMPshop that is GIMP made to look and feel
If you have Photoshop, use it. If you don’t have access or are just
learning/experimenting with computer editing, GIMP is an excellent
tool to try out for free (free as in beer and free as in speech),
and many of the tools are common to image manipulation software and
the skills learned translate to other programs such as Photoshop.