My opinion would vary based on how long-term you expect the job to be.
If this is a 1-year job that you're already part-way through, and you're looking for a serious relationship that you fully anticipate will last longer than 1 year, then it's probably OK, provided it's within the rules of the workplace. However, be aware that you're at a great risk that your approaches will be unappreciated and you'll be reported for harassment, so move slowly and make sure you're both on the same page before moving forward. Also be absolutely certain it's allowed. Furthermore, best if the person is not a close associate (not on your team/in your department), and be aware that you will both likely be held back from any promotions that would make one or the other in a supervisory role that was above the other person's level.
If this is a longer-term career job, then don't risk it. Just don't. Relationships usually don't last, and a break-up while you both work at the same job will create waaaaay more problems than getting together while you both work at the same job. I know initially you both really like each other and you think this one's “the one” and whatever, but it might not be, and it's not worth the risk. If you like them that much that you're that head-over-heels, then find a new job, and ask them out for coffee later.
Full disclosure: I'm dating a guy I met at work. We started dating while we worked together. But, it was when we both worked at a grocery store. It was a short-term job, and I knew it. We became friends, and then it changed into a relationship, but our job was just a job, not a career. Five months into our relationship, I got a new job – not so much because we were dating, but just because it was a short-term job to start with, and its short-term was over and I was on to bigger and better things. Now it's years later and I'm into a career and we're still together – the relationship lasted way longer than the job for both of us. But, if I was single now, I wouldn't date someone at my current job, cause this job is a career job, and the risk is too great. Yes, I meet lots of nice people here, but a breakup here could leave me out of job and love, and that's not a good spot to be in. There's lots of people at work, but there's lots of people not at work, too, and you're better to find love from the not-at-work people.
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