Aren't those fanatastic? I bought one a couple of years back (was dating a woman who did photography... didn't want to buy it for her, but though it was cool and I could "loan" it to her when she needed it). I use it a lot, mainly in CorelDraw or Corel PhotoPaint, though I've been led to believe that it's possible to use one of these in ZBrush (haven't figured out how yet... but I've barely learned my way around the UI in ZBrush and can't really do anything in there anyway, yet!).
I got the 8x10 version... the pressure-and-angle-sensitive one as well. I only have the basic "art pen" and the mouse (both of which came with it) but I've been thinking that the "airbrush" might be useful... it works a lot differently than the pen and it's hard to get the "airbrush" functionality to work well with a pen, I've found, in Corel.
But once you've used a "pen" instead of a mouse to try to draw... you can never go back!