Real coincidence. I met for coffee with a writer friend just this past Wednesday. She pulled out her new Samsung Galaxy Note phone. (to add to some notes she had made at work) I commented on it re: looks like it would be great to sketch on, seeing as how fluid the pen was. She was saying her partner uses it to sketch on, she had the sketchbook pro app on it.
I tried it out and OMG, so FAR superior to using my ipad and jot pro stylus that there is just no comparison. In fact, I hate to admit it but, it is exactly the same feel as working on the cintiq, and there is NO lag time, none, not like there is on the Ipad. I am an Apple FANatic thru and thru but, this is a fantastic sketching tool! It is, however, a small surface (though larger then the iphone certainly) and it would be crazy to try and do a whole Illustration on it, the scrolling would drive one mad. But, if an Illustrator were considering a new phone, this might be a great idea for portable sketching.
It can't replace the cintiq of course for full art (nothing can:), but it's pretty darn cool!
(as an Apple share holder I can NOT believe I am saying buy anything other then an Iphone:)