I don't have experience working graveyard (3rd shift / overnight), but I have been working swing shift (2nd shift / night) for about 18 months now.
There are upsides and downsides to working 2nd shift. Upsides: that the hours are somewhat closer to what most other people are used to (you go to work during the day and leave at night), you have time for errands before work, and traffic is usually a breeze. Downsides: you can't do much anything after work (save for visiting whatever 24-hour businesses are in your area; Wal-Mart is my freind), socializing after work isn't going to happen unless you hang out with co-workers or know anyone else working your shift.
Shift work will change your perception of time. Basicly, your ideas of "morning," "afternoon," and "night" will become highly elastic. During any given 24-hour stretch, you'll find yourself working about 9 hours, sleeping about 8 hours, commuting however long, and the balance is your for ... whatever. Assuming you get back-to-back days off, your "Saturday" and "Sunday" may not fall upon said days of the week. My weekends are Friday/Saturday. Every time a new schedule comes out, the question is inevitably asked: When's your Friday? ... with the answer typically not being "Friday."
I've been fortunate to have a stable schedule for so long. I work from 3PM - 11:30PM. If I'm feeling ambitious or have some errand to run during the day, I get up around noon and head into work around 2PM (Dallas traffic being highly variable). I leave work at 11:30, get home around midnight, and try to turn in around 4AM. I'm accustomed to the hours now (sort of like being in college again). Any caffiene I ingest is more compensation for poor sleeping habits than anything else... I'd like to get onto a late-morning shift (10:00AM - 6:30PM) since working "Seconds" is slowly driving me nuts.
Some people like working third/overnight shifts instead of second shift... At the end of the day you can go out and do things, which seems to work better than trying to run errands at the beginning of the day.
Wherever you work, I hope it's a more 24-hour friendly place than Dallas, which seems to roll up the sidewalks around 9PM.