I'm no heavy Photoshop user, but for basic stuff The Gimp works fine. Interface is a bit different, neither one seemed harder to get used to, but if you're well-versed in Photoshop, then there may be a bit of a learning curve you weren't expecting. As an added bonus, if you ever decided to switch from Windows to Linux, that's one more program you don't have to worry about (The Gimp runs on Linux without any extra work, same as OpenOffice.org and Firefox).