I have never had good luck with my Wacom Graphire 2 and GIMP. The biggest issue I had is the Wacom stylus not giving a continuous registration while making smooth strokes, but instead making squared off input. I was able to solve this by using a newer Wacom driver, but that driver makes my WinXP slow to load up unfortunately.
Between GIMP and Elements (I have v2), I still choose Elements due to the better brush mangement for my purposes.