Holy shit.. I'm still using version 5. I saw a mixed bag of reviews on amazon since Corel took over the title and have been reluctant to upgrade. I'm using Gimp for windows for a lot of editing work and so far that's been as good as PSP.. free too.
I don't do advanced anything so I use Corel Photo Paint that came with my Corel Draw. If you feel like making an investment into an entire package, get Corel Suite X3 or X4. Corel Draw(IMO) is much better and user friendly than Illustrator and Photo-Paint is pretty good even though Photoshop is superior.
I just upgraded to Paint Shop Pro X2 and I love it. The HDR photo merge is great. They changed the background screen color to a gray which makes it alot easier on the eyes. Still works with Photoshop plug ins too.