Multi touch is available on the newer macbooks via the trackpad - I dont think its a big jump from there to touch screens.
Yes it is, and it works better than on Windows 7 but its key benefits lie in handheld devices. Vertical screens and touch technology for home use or chronic work use do not go well because our anatomy and physiology works against it. Holding your hand eye level leads to fatigue and other issues.
eg Gorilla arm etc.