I've been a Wacom tablet user for at least 15 years (started with a Graphire and moved progressively up to the Intuos4 large). I was fairly used to the hand-eye disconnect that comes with a tablet. But last year, I took a leap of faith and purchased a Cintiq (mine is a 22hd).
It's been very worth it for me. Is my art better? I believe it is to a small extent. But the real benefit is that I now draw and paint on screen just like I do traditionally - by watching my hand and the marks I make on the surface. As far as I am concerned, THIS is the way digital painting should be done.
I'm in the process right now of selling off my Intuos4 Large, because I don't see myself ever returning to tablets.
Last night I slept like a baby: I wore a diaper.