There's a cost to it, but the latest version supports Photoshop 7. They're not sure about CS or CS2 yet--these might run as unsupported software.
As for the GIMP, IMO it was designed to be a casual-user replacement for Photoshop--and not intended as a replacement in professional use.
Here we run into the difference between the person who suggests the practical uses of OSS and the zealot. People are out there right now trying to use Gimp for pro work, but they suffer in quality ("I don't care if the color is a little off") and expense by having the service bureau do the final-stage Photoshop for them to make it ready for print.
From the service bureau side, it's about as annoying as those who send for-print jobs in Microsoft Publisher.