I've been using tablets since (OUCH
) before the pens were wireless! The biggest boost comes from actually drawing/sketching IMHO -- maybe it's because I'm an ol'fart, but I've never been able to duplicate the results of using a pen/pencil using a mouse. If you're doing something like re-touching, being able to taper the stroke using whatever filter or brush, I think just can't be done otherwise.
When/if you're just moving pixels, a hi rez mouse is usually less trouble, though some people just feel a pen is more intuitive. Personally I've found that if I've been using a tablet a lot, the mouse feels like I'm chipping away at one rock with another -- until I've been using the mouse again for a while.
Same sort of thing if I've been using a trackball, so a lot of what you might hear from tablet users is biased by what they're personally used to at the time.
A couple of versions of Vista have a neat handwriting recognition program for tablets, but I've yet to find a practical use for it *for me*.
Wacom tablets are great, but pricey. Aiptek tablets (actually Waltrop I think sold under a LOT of names) are give-away by comparison... If you can catch them at Aldi's, they sell a Medion (identical to the Aiptek 12000U) for ~$30-40! The Aiptek's pen seems crude by comparison, and doesn't do the same tilt stuff like a Wacom, so if you're really trying to imitate paint in a program like painter, you'll probably not be satisfied. If you use it for photo touch-up or similar, that tilt stuff isn't going to matter. Personally I've never seen a huge difference using the Wacom's higher number of pressure levels, but maybe I'm just not that fine enough of an artist.
Wacom has better drivers, but, most everything I've tried recognizes and works with the Aiptek as well -- there are probably zillions of these things out there under different names after all. Construction can't compare -- I can't help but feel the need to be extra careful with the Aiptek, but that's just a reaction to the way it feels so light. It's either on my desk or leaning under it, so how sturdy the tablet is is pretty irrelevant. At the end of the day for what I use it for I just can't justify hundreds of dollars vs $50, so I can't truthfully recommend Wacom unless there's something absolutely critical the Aiptek just won't do.
BTW... Aiptek.com sells pens for $10, and the newer style is supposed to be better.