I used PS Elements 6.0 because it went with my tablet but I dont like it much...some essential things from the full PS are missing...
I recently got PS CS3 and Im so very happy with it, now I dont have to use Gimp (2.0) for making linearts...tho Gimp sure has some nice brushes its just too circuitous for me.
My very favorite program is SAI, its simple and quick to use and has just the right brushes (e.g. water) I need for my favorite coloring style...sadly I dont have the money to buy it =(