I got the Wacom Intuos 4 (small) about six weeks ago.  My incentive was the handwriting support in Windows(XP forward).  My idea was to use it to replace both the keyboard and the mouse in everything.  (After twenty five years of working with computers, this lurch from familiar methods was irrational, not considered.)  I was incredibly lucky.  I have uninstalled my mouse, and stood the keyboard against the wall behind my desk. 

Caveats:

1.  Take the learning curve advice folks have mentioned seriously.  You need to train your reflexes to a new landscape.  But it is worth it.

2. Train the Windows input programs to your handwriting style.  It really works. 
   3.  Poser, my only graphics toy, was the hardest program to get used to.  There is a 'latency' of a fraction of a second in touching elements or dials, and I think the 'pressure sensitivity' technology affects the results here (It is useless in Poser, but is inherent in the technology.)  However, with practice you get used to the 'feedback' and it works perfectly on dials and the work area. 
   4.  The camera problem mentioned by the other folks is real, but is, I think, part of the learning curve involved in adjusting to the touch sensitivity of the technology.  It was for me.
   5.  I wrote this on the Wacom.