Art programs? Hmmn, well I started off with Gimp for the first year or so when I first got my tablet. I then moved on to Paint Tool Sai a little after that. Then this past Spring I got Photoshop and have happily been using it since!
Paint Tool Sai used to get a little weird with my Tablet so I had to reinstall it a couple of times but other than a few hiccups here & there, those 3 programs worked like a charm!