I have a Wacom (I think it's a 4 x 6") that i've had for a couple of years now. I use it mainly for freehand drawing on things- as it's easier to control than the mouse. It takes a little bit to get used to since you can use the pen in place of your mouse, but it is more precise. It takes some practice to get the hang of coordinating the placement of the pointer on the screen with "drawing" on the table, but it's easy to pick-up. Once you get used to the feel of it, it's really quite useful for detail work since you can adjust the pen "pressure", much like drawing/painting in real life. The following image I did for a class a few years ago, and I think it's the first thing I did with the tablet. I "traced" the outline of the building in the image and then used various paint brushes to fill it all in using the tablet. Not that great, but it much easier than trying to do it with the mouse.
I highly recommend it - and definitely bigger than the one that I have. I think that you'd find a ton of different uses for it.