I wouldnt say its a must-need, it depends on what your doing, if your drawing, painting textures, or pictures, photoediting, sculpting, then yes you should use one. If your animating, scripting, setting up lights, you could do w/o one.
graphire4 from wacom is the cheapest option i know of, it seems nice, i had a graphire3 a while back (sold my intuos2 and bought that) and it wasnt as nice as the intuos2 but was ok to use, now that i have an intuos3 i cant imagine using anything else.
if you just want to know if you will enjoy or benefit from using a tablet, then buy a graphire from wacom and see how your liking it, if you want the best experience first, then try the intuos3 as it will only make you happy. i have the 6x11 (widescreen) but the 6x8 is a good option as well, and under 300. i cant stand anything bigger (friend of mine has the 9x12 and he never uses it, and i tried using it and its just way to much work to use).
good luck
Also, be sure to ask them to ship it to you via USPS and not UPS because UPS tend to charge a very hefty fee. Good luck with your tablet hunting.

