I bought my tablet after people swore by them. I don't use it as much as I should - mainly through laziness. It's generally when I need to use freehand strokes the tablet comes into its own, but for general menu selection actions, I'm more comfortable with the mouse.
I've got an A4 Wacom, but in terms of the amount of room it takes up on the desk, I think I would have got an A5 in retrospect.
Hope this helps.