I have the Intuos3 6x8. It fits nicely in my laptop bag and is easy to take everywhere I go.
There are just some things in PS that you need a tablet for and some things that take half the time using a tablet. No matter how good a mouse is, it won't give you pressure or angle control to shape a brush. I use the tablet mainly for masking work, as well as the usual healing and touch up on portraits.
The other nice thing with the Intuos3 is how customizable all the controls are. I have one touchstrip set to zoom in and out and the other to control brush size. Other buttons are set up as Undo, Space Bar (for moving), Clone Tool, Healing Brush, Shift/Alt for selections, and Sample . So most of the time I never have to even touch the keyboard.
Granted, for most of my PP work I only ever use C1 and prefer a mouse with a scroll wheel over a tablet. But, once you get accostomed to the control and finesse of a tablet, you won't want to go back.
David