I rarely use tablets myself, but our senior editor swears by his and has pretty much abandoned his mouse completely. We bought it for one particular job that needed tons of rotoscoping, but as it turns out he is now using the tablet for pretty much all computer control (I had to look for the mouse the last time I was on his system).
We got him the biggest Wacom that would fit on his desk. It's about 12x19" or so... I'm not sure if that is the very biggest Wacom but it is definitely one of the larger ones.
When we decided to buy him one I was surprised that they were pretty darn affordable. I don't remember exactly how much it was, but it was in the "few hundred bucks" neighborhood... definitely less than a grand, and it seems to work like a charm.
Fantastic Plastic Entertainment, Inc. fantasticplastic.com
I bought a 12x18 Wacom tablet when they first came out to use with my Dubner TurboPainter. I liked it but found it to be a bit large. Then we went to Discreet smoke and fire and got 6x9 Wacom tablets and I have found them to be a great, usable size. The 6x11 would be great for widescreen apps. The large one took up so much space on the desk I couldn't do anything else so I've taken it out of service and will be glad to sell it for cents on the dollar. That includes the really cool wireless 5 button mouse.
fire*, smoke*, photoshopCS3
Charlotte Public Television
del underscore edits at wtvi dot org