1) I was referring to portable all-in-one units like the Boss Micro BR, Tascam field recorders, etc. Maybe I should have been more explicit about this.
2) Ableton is great for recording and processing, but for creating virtual instruments without external hardware, I'd prefer the iPad interface.
What do you mean by "creating virtual instruments"? Do you mean presenting a virtual instrument interface on screen? If so, I do think the touch surface has some real advantages over a mouse.
I'm still not sold on virtual keyboards and drum surfaces on touch screens though. So far I haven't seen one I'd prefer to a real midi keyboard and drum pads.