It works well for me. I'm not fast to fall asleep, so I started using it a couple years ago when I had several short (6 hr) redeyes. It works well, gets me ~5hrs of sleep, and doesn't give me a hangover. No reports of strange (or stranger than usual) behavior.

I got to test the "what if I really needed to function?" scenario last summer, when I took it when I boarded, but then took a VBD: I had to get off the plane, get my negotiated payment, get rerouted acceptably, go check in with another airline, and kill four hours in the airport. I was spacy--no driving--but not worse than being a little drunk.