There is definitely a learning curve with drawing tablets. Some photographers love them, others hate them. Full-time retouchers seem to praise them more often than photographers, but again it is a preference. In my experience, if you are doing a lot of photo-illustration where painting techniques apply, then you will likely benefit. Photoshop has built-in features such as pressure for variable width brush strokes that add sensitivity one does not have with a mouse.
FYI, I used the Wacom Cintiq for awhile which changes the game if one can afford it. Cintiq is the new line of HD LCD tablets if you can imagine drawing directly on a large iPad screen, for example. It's more intuitive than the popular Intuos tablets that are the industry standard, but costs $1000-3000 depending on size. You use it much like a second monitor. The new Companion line recently announced are actually Windows or Android mobile tablets themselves. On the other end of the spectrum, a cheaper alternative to Intuos tablets are the ones from Monoprice.com. For under $100 they are hard to beat.