I've not long finished a week of working at night. This is something I've never done before and I have a few thoughts about the concept.
Basically, we're not nocturnal creatures. I found the working at night/sleeping during the daytime lifestyle felt very unnatural - by about midway through the week in question, I had no idea which day of the week it was, I really found myself feeling very disoriented indeed. Even by the end of this time I never really got used to sleeping during the day, either.
I know people who do shift/night work and some of them seem to cope well. However, I'm not one of them and I won't be sorry if it's something I don't have to face again any time soon.