i have:
http://www.bytewizecomputers.com/pro...7/37/477/10030
it's the 6x8. perfect size. it comes with a mouse too so you could get rid of your other mouse. theres 2 buttons on the tablet itself (programable) and a scroll wheel. on the pen, theres the click, rightclick and double click i think? plus the eraser. so over all, i recommend this one. if you don't use it that much, some people will say the 4x5 but i still say go for the 6x8 because it's much easier to draw in there.
if you have more money, you could get the intuos3.
http://www.bytewizecomputers.com/products/7/37/477/6970
they have more buttons and i think the tilt on the pen. I personally don't know if it's worth it.