based on the latest review it seems like the screen is the only selling point
there's some super small touchpad-like tablets from wacom if you need something really portable, but i advise sticking with the wacom brand while avoiding the bamboo line in general. they have the most consistent and best reviews overall iirc
as for portability, my intuous pro medium is slightly smaller than an old 16" laptop i have. a small will fit in a standard backpack easily.