... the same goes for Milkshape, and just every other 3d modellor.
for the sake of accuracy, Maya has this feature. but painting on a 3D model isn't all it's cracked up to be. it's okay for broad sweeps of color, but on generally low poly models, the kind of detail i've wanted on a skin to mask it's low polycount lends itself better to regular old 2D paint programs. while i haven't tried it, wouldn't surprise me if Tattoo provides just as much functionality as anything you'll find. but don't expect to avoid the detail work for most objects.