i've been a graphic designer for over 10 years now, and 4 years ago, i switched. over the past 4 years, i've used both the wacom graphire (bargain basement version) AND the wacom intuos (higher end -- what i use currently).
that said, i can tell you these important things...
-> the learning curve from mouse to tablet and stylus is a couple weeks, TOPS. (more like a couple days, really.)
-> pulling points (such as in illustrator, or pathing in ps) is about seventeen THOUSAND times easier with a stylus and tablet.
-> higher end tablets (such as the intuos 3 and above) offer built-in macro keys, which you can use with your fingers or with the stylus, and which, when programmed with savvy, can make your life a lot easier. (consider zooming in and out on a photoshop doc by simply sliding your stylus on a small pad to the side of your main tablet area.)
-> the tablet's "work area" is automatically mapped to the aspect ratio of your screen. thus, there is no more of that "move-pickup-move-pickup" thing that you have to do with a mouse.
-> the "posture" of your hand, when using a stylus, is far more natural than with a mouse, and thus, more ergonomically correct.
i resisted the switch for about a year, and finally "gave in" only because the pain in my forearm was starting to get worse and i realized i really needed to do something. once i made the change, i found that not only did my arm not hurt anymore ... like, EVER ... but i had unwittingly stumbled across the single greatest interface peripheral ever invented.
obviously, it comes highly recommended from this kid.
hopefully, this is helpful.
blair cerny | sf.ca