I have the Wacom Intuos 3, 9x12.
It does work nicely (IMHO…) if you have a monitor with a viewable display to kinda match your 9x12 active area on your tablet, as your eye to hand coordination will feel more like 1:1 ratio from the tablet to your screen.
And/but, the tablet is HIGHLY customizable in all areas. Experiment and get it to react just how you like, pretty much no matter what you have your desktop resolution set to, OR even to what your document is set to in ZBrush.
I will say it WAS more work at first to do everything since I was using larger back and forth hand motions than I would do with the old wrist movement and a mouse. But, eventually you get used to it. (and, I still am, being new to my tablet and ZBrush)
A 9x12 is a little large to have on your desk or to prop on your lap, BUT, that size is very nice when working with ZBrush, or just painting. It’s worth it, imho.
AgentSmith