I've used Paintshop Pro for years now. Currently use Paintshop Pro XI in my photography workflow and I like it. I've used both programs and you'll find they both have the same capabilities with Paintshop offering more graphic/vector options. It's hard to justify the price of Photoshop, when you can get a program thats does many of the same things at a fraction of the cost.
I will say this tho, PSP 11 has not been without flaws (recently updated), When I had version 8, 9, and 10, I never had an issue.
good luck