Cintiq is the best you can get. I have worked with those for a couple of years... But they cost a fortune.
Now I have a Yiynova Msp19u+ at home and, despite some driver issues and a lower resolution screen and a not-so-good viewing angle it's awesome for the price. I draw comics and shit on the side and the Yiynova is faster reacting than the Cintiq. For a third of the price!
If you're not a professional graphics artist or photographer that needs a 100 % accuracy on colours, go for the Yiynova.
Oh, and I have an older Yiynova. There is newer with bigger and better screens, but I haven't tried them, so I cannot vouch for them.