If you are actually going to sketch and draw with it then it might be worth it. Because you can more easily get a freehand feel with a tablet, than a mouse.
But I and many others I know who have been using photoshop and other similar programs prefer using a mouse. I used to employ a few photo retouchers, one of them used a Wacom tablet, and got excellent results. But they mainly seemed to use a mouse.
I still have the tablet, but I never use it. Mainly because if i want to draw something, I draw it on paper then scan and edit it with the computer. I get a better freehand feel from pencil and paper and the tablet doesn't give me the precise control that I can get with a mouse.
I will now open the floor to the tablet devotees who, I am sure, can't wait present their re-butts