I am a Windows user using Paint Shop Pro and have been for a number of years creating my cartoon art (Check out:
http://www.eejits-online.co.uk). I'm so ingrained into my work process that it's probably the only thing stopping me from buying an iMac. (The reasoning being why spend £1500+ on a machine to have to Bootcamp and run Windows on it. I might as well stay where I am).
I've been watching Pixelmator with interest though. One of these days I'll push myself to make the jump.....
If you do make the transition to PixelMator I'd love to hear your thoughts and how easy it was to move from Paint Shop Pro.
(BTW I asked Corel if there was ever going to be a Mac version of Paint Shop Pro and they said they had no plans to, and instead to run Windows on the Mac to access PSP)
George