I'd like to find something that's still pretty light and small, and able to carry around in my messenger bag. I've considered an android tablet but I haven't been able to find any with a pressure sensitive pen (an absolute must for me- I even tried the Samsung Galaxy pen but the built in paint app didn't show too much promise)- that tends to disqualify the iPad for me too unless they have a pen that feels like a wacom now. There's a Colors app for iPad but iirc it involves tilting the pad and painting with your finger, I'm not sure I could get used to that.
That leaves me thinking about the eeeSlate- which is frighteningly expensive, but might enable me to also use ZBrush on the go (which would be a huge plus).
For now, I'm mostly interested in finding a better setup to paint on without sacrificing the portability I've been enjoying with the DS, perhaps someone knows of some good suggestions?