I'm strictly a hobbyist level artist, however, I just got a Motion LE1700 which is going to be pretty much strictly an art machine. I haven't done much with it yet because I just got the screen protector today and I've been out looking at houses all day (And taking notes on them with onenote).
It's a pretty awesome tablet for art, IMO. The slate form factor is good for carrying around and doodling, and it's got heavy enough specs to run modern graphics apps with no appreciable lag.
I heartily recommend ArtRage as an art app, by the way... I used to use an OpenCanvas->Painter->Photoshop 3 step process for artwork (Sketching in Opencanvas, making the actual painting in Painter, and then cleaning it up in Photoshop) but I'm thinking ArtRage may actually completely replace all 3 of those for me.
I will say... That if I had the money, I probably would have bought the TabletKiosk Sahara i440d instead. The N-Trig digitizer is slick, and gives you capacitive touch in addition to pen. But it's too expensive for my wallet so ;)
On the other hand... If you need to use Photoshop, you should probably pass on N-Trig based tablets, unless you can live with using Linux as your OS and running Photoshop in Wine, because that's the only way to get the N-Trig digitizer to provide pen pressure sensitivity to apps that use the old Wintab.dll interface, like Photoshop.