It kind of amazes me how many people have said they couldn't get used to it. I worked a 9 pm to 6 am for three years and took to it right away. I guess we are all different.
The hours eventually morphed to a 5:30 pm to 2:30 am shift and that was even better. I would work that shift again in a heartbeat.
That said, for the last 18 years, I have been working four 10's, 5am - 3 pm. I still haven't adapted and have the worst time getting up at 4 am, even after all this time.