Third shift is never good.
In addition to the Graveyard Shift, it is also sometimes called the Night Shift, a nickname it sometimes shares with second shift. Note that I cannot fall into the regular third shift pattern because I am a swing shifter, which means they toss me all around the time clock, and where I work, you can literally see me at any time of the day, because we never close, not even on Christmas Day.
Third shift will screw with your sense of perception. The thing of it is, someone will ask you for the date, and you might not be sure if it is still today, or if today has become yesterday and tomorrow has become today. As passport noted, you will often be around artificial lighting. You put up a fight with your own body, (it gets especially hard around 4:00 am) because humans are not nocturnal creatures. We were meant to sleep at night. And working third shift pits us against this natural urge.
There is an old saying, the freaks come out at night. At my job, I have seen this proven true. People come around, either going to parties, coming from parties, or in between parties, wanting beer, and big fat cigars which I know they are just going to take the tobacco out of and fill with marajuana.
Third shift is frequently performed by nurses, law enforcement officials, truck drivers, and other people who work places that stay open 24 hours.
Third shift damages your days off, (maybe it's extra hard on me because I swing the clock, I can't say) because even if you are off a day, you have to sleep for half of it!
I agree with passport, third shift is great if you are single. I am, plus I have no social life, so I can get on okay swingshifting for now, I just stay kind of tired when I work a lot of third.
There is also the increased danger of being robbed or something on third shift, because of the dark and lonely hours. This has never really bothered me, I go outside and change the trash and all, and I'm not worried about getting hit in the head, but that's not to say it couldn't happen.