As far as I know, Gabe uses a Cintiq, so he's drawing directly on the screen.
He does not. The PAX DVDs and PATV episodes show him clearly using a very large Intuos tablet. It seems to be that he just prefers it that way.
Jeph from QC, Kurtz from PvP, and Gallagher from MT all use 21UX Cintiqs, AFAIK.
I picked up one of the older Cintiq models off eBay for about €300 a couple of weeks ago (The new ones are in the €2,000 range over here), and it's fantastic. It's only got a 1024x768 screen, but the whole 'not looking at your hand' disconnect is completely abolished. It's got a 15" screen, so it's about the same size as standard copier paper, which was what I was using before. It's basically my most fun toy (I've got a PS3, but not a sex swing).
I have noticed that it really rewards quick pen strokes. Doing a quick slash with the default brush gives a nice smooth controlled-looking line, and I guess practising up on that will ultimately lead to better-looking comics with a shorter production time (I currently draw lots of little lines to make a big line. Since getting the Wacom I've moved the 'undo' function in photoshop up to allow for the last 220 moves).
I find that interesting. I have a 21UX that I got a month ago, and have found I can actually draw much slower and get good, interesting, detailed lines than when I was using my Intuos 3.
In any event, the Cintiq I have now is pretty darn awesome. I'd be really sad if I had to go back to an Intuos (if for no other reason than I can work at a lesser zoom ratio, so I can see more of my artwork when I work on it, and there's zero need to mess with matching up the tablet and screen proportions).