I've worked with too many couples who have been unable to keep their personal life to themselves. Some of them are happily married now, few of them split up while they were both working for the same company.
In most cases the couples tried to be discrete but it was blatently obvious to everyone else. I remember one couple who genuinely thought they had been so discrete that none of us knew at all. After 6 months they finally came out in the open and we all breathed a sigh of relief as it had been a nightmare dealing with the fall out from their arguments when they weren't officially a couple, so we couldn't say anything to them.
You can't chose who you fall in love with, but if I ever fall for someone in the same workplace as me then I would be quickly looking for a transfer. Preferebaly outside the company, but certainly outside the department.
Something else to consider - and I've known this to happen to three couples, when redundancies come around, the people makeing the decisions won't take into account the fact that they are taking two incomes away from you. Better not to have all your eggs in one basket if you can.