Well, i personally use my wacom for painting textures, 3D paint, paintFX, etc.
I don't use it much for modeling.
I know many others who cannot live whithout it, and some who don't use one at all.
It's personal preference I guess.
For the overlay stuff, check out the wacom instruction booklet, or cd, as they talk about how to configure your tablet to do some nifty things.
(I don't do the overlay, so I'm not much help there)
Welcome to SM by the way!
Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS