Hmmmm Wacom has a new fully portable Cintiq coming out - the Companion 2. Works with W8...not sure how I feel about that but still would like to check it out. I'm using my iPad for my drawing-on-the-go, but all about my Wacom at home. Some of the iPad apps are great, and although some styluses are better than others, it lacks precision.
As a sidenote, I do have an older Cintiq at home, but I never use it. I prefer the Wacom tablet, because my hand is invisible.
Above image from the Wacom site.