It'll be nice not only for the blind (assuming Braille or something comparable is feasible with this technology) but for those of us who'd like to be able to touch-type, which is tough with existing touch-screens.
This is at least my experience with little cellphone hard-keyboards, maybe it's different for others.
Regardless, braille would be really cool. Assuming the screens were high enough resolution (that is, could raise itself up accurately enough to make small dots) to display it.