The Gimp or Gimp shop can produce the same quality work as Photoshop, I personally love gimp i've used it a long time since it comes bundled with most Distros of Linux, its also as extesiable photoshop with its "Script Fu" so if you are looking for a cheap alternitive to photoshop I highly recomend Gimp, although the interface may take some millage to get used to, try Gimpshop for a friendlier interface with all the same feature's

I own Photoshop CS3 and still go back to gimp a lot, in some ways its more fun to use as well.