great thoughts in this thread so far... I've got an Intuos 4 extra large tablet and stylus that I've used for the past few years. I would have bought the large instead if I were to go back in time. The last shop I worked in had the tiny 6" square tablets that were a little too small...I went to the other extreme but now I have to move the stylus across more real-estate to get the effect I need. I've gotten used to it and it is more helpful in small detail situations.
Every review I've seen mentions the disconnect between pen and result (when using the stylus and tablet) slows down production and that the real-time effect of the cintiq (or applicable draw-on tablet) has a positive change in workflow.
I've been wanting to purchase a Cintiq myself, though its not been in the budget just yet. There is a new 27" model coming out in July. I've been debating whether it was better to get a smaller more compact and mobile unit (cheaper also) or invest in a unit that allows for greater space? I don't travel much with my work.
I thought the bigger one would be the best way to go, may still feel the same way later. But with a small shop(just the 2 of us) most of the drawing/design work only happens at the house. In the shop it's go, go, go in every direction besides the computer.
There are things I do not like about this little cintiq, like the way the cords are set up. No real time spent on it so besides that it's very nice and responsive.