I bought the Waco Bamboo pen tablet a while back and like it. My particular laptop has a touch-pad mouse and it's not very accurate for image editing. I think that I could do the same thing with an external mouse on a solid table, but I do most of my drawing and editing sitting on the couch while watching TV, so the tablet does help.
Maybe you can meet up with someone that owns one and try it out before you buy one. That is often the best way to determine if something is going to meet your expectations. Best Buy has them, but they are not on display for testing like some items are. There is also a learning curve to using one. It took me a few days to get the hang of positioning the stylus pen on the tablet to coincide with the computer screen.
As you probably know, zooming in to the subject and working on small areas at a time will result in more accurate images. If you take your time, I suspect you will get similar results with a regular mouse on a solid surface.