Hiya, only just started with Zbrush, alot of people seem to have Graphics Tablets, should I get one and which to go for?? 
Welcome aboard Gareth,
There are a lot of people who make great stuff with Zbrush without a tablet. It is definetely not a necessity. But having said that it becomes a necessity once you have used one for a while.
The main benefits for me is of course the pressure sensetivety, which is especially useful when modeling. You will still need to adjust the draw size and Z intensity once in a while, but it gives a much more natural feel to the modeling/sculpting process. Zbrush benefits from the pressure sensetivity much as Photoshop does.
About the size, it really depends on the depth of your pockets. I’ve got a 9x12 inch wacom and sometimes I feel it is too big, sometimes it’s perfect. Try drawing the sizes out on paper and do some arm movements across it. Make sure nobody is watching first 
Should give you a feel for it.
If I had to buy a new one, I would probably go for the 6x8 inch intuos2 (I’ve got intuos1) that size should be quite comfortable to transport around. But having said that I still have my Wacom PenPartner A6 sized lying at work and it gives fine results.
But these suckers are quite expensive so read up on them first and shop around. Also check out the threads in the Quicklinks section(top of the page). There are 5-6 threads linked regarding tablets.
Edit: you can also try messing with the Preferences 
Draw Mouse Averaging before deciding. Works great with 2d drawing can’t remember how it stacks up when modeling.
Thanks for the info, Wacom costs a bit to much for me at the mo, the do lok very nice though!! Cheers guys.
you could buy the small graphire from wacom, thats relatively cheap. its pretty small, but suffices (i do habe such myself)