I couldn't see myself being able to fall asleep in one of these, I have alot of difficulty sleeping in unfamiliar/new places (my lifestyle doesn't work well with that anyway).
I would, however, love to be able to take a good, long shower (20 min+) after a long flight. Anything more than 5 hours and I feel like crap and am longing for a shower. I was going BRU-IAD-PHL and had a long time in IAD. I would've paid quite a bit to be able to take a shower.