I say it all depends on the work environment. It has advantages and disadvantages.
Disadvantages-If you break up you are stuck seeing them everyday. You could become the watercooler gossip. Everyone would be in your business. You are stuck around them most of the day, so when you get off, you loose that "Me" Time. If the person is your boss, you could loose friends, and become the subject of catty gossip, even your raises will be questioned, same as if you were the boss and dating an employee......it just opens a can of worms.
Advantages-You save on gas, you could carpool lol.
If it's a good relationship, you could do a romantic lunch, it's like going on a date mid-day. If you hate your job, it gives you a reason to come to work :)
Before you decide on pursuing anything I would check company policy. Second determine if this person is worth it in the long haul, because what if you casually date, and find out they don't want to pursue it, would it affect you if they started dating someone else in your office?Also if they are in a relationship don't do it, if they are willing to cheat on someone else to be with you, what do you think they will do to you? To each their own, I would suggest writing a pro and con list, and then make a decision from there.