I have a Wacom tablet on my Mac and a tablet PC.
I'm not a graphics designer. In fact I can/t really draw very well and I work very well with a mouse. Still for getting shapes into an application it's very efficient. Take a simple thing such as a signature. You could sign a paper, scan it, then convert the bitmap to curves, and fiddle with splines line weight, pen angle, etc to get something close. Or you can just open Illustrator and sign you name and have something that's nearly perfect in vector form. The pressure sensitivity of the pen is a real nice feature for things like this.
A Tablet PC is just a normal PC with a Wacom digitiser sandwiched with the LCD. They come in two types, pure tablets, and convertibles. Pure tablets are usually under powered with a short battery life. Convertibles are simply overweight. Both are over priced, at least compared to a similar notebook.
I chose a tablet over a convertible because of size and weight. It's like having a thick clipboard. The ability to print something to journal viewer, annotate it, and hand it across the table to a client is simply incomparable. In places where you have to work standing, or can't spread out and set up a mouse having a stylus is much more efficient than a touch pad or a tit. It takes some getting used to, and for someone who types faster than most people think the handwriting input can be a bit tedious. If you need to type a lot while the machine is not in a docking station or some place you can set up a keyboard then you might want to consider a convertible.
