Something about this program felt really nice to me. As soon as you open the program you can immediately start scribbling and I got this instant sense of, "Oooh, look at that."
I've used Corel Painter before too -- do I own it? I have to check, I think it came with my tablet. I can't remember. I definitely need practice with the tablet.
I'm not even using my tablet with the demo yet... this is just quickie testing with the mouse, and even with the mouse the strokes feel and look nice. If you go really fast you get a drybrush effect at the end of a stroke, etc.
Best of all, it's free! Well, there is a free version anyway, and aside from a few missing tools you can do all the key things. Save, resize, yadda. No icky watermarks, so I wouldn't call it crippleware. The full version is a whopping $19.
Here's a Bob Ross style tutorial I found for ArtRage.
Of course, for $179 I could get Autodesk Sketchbook Pro, which I heard about via Penny Arcade. Reportedly that's more of a drawing program. Here's cartoonmonkey's blog entry comparing the two.
I'll try a demo of that too, see which of the three programs (ArtRage, Painter, or Sketchbook) I like more.