I think tablets are good in pixel drawing too, because it's more accurate to draw with pen than mouse. But some programs don't support tablets (at least not all features like pressure), like my own tile drawing program Stile.
If you plan to buy one, get Wacom. I don't know why other manufacturers don't make pens that run without battery, but that's really good thing. Bad thing about Wacoms is that they cost like bananas, but if you don't need sophisticated features like tilting then buy the cheaper Bamboo model. Also, you don't usually need a big tablet. A5 is fine.