This is how I look at it:
How well are you at not getting uncomfortable? I'm going to say this as a serious similar action... Recently I participated in a threesome with this guy I hang out with. The next day he couldn't look me in the eyes, he was very akward about it.
I don't believe having a relationship with a coworker complicates work or life, in fact it might be more convenient. You'll enjoy working better, you'll get to know your soon to be girlfriend better, and you'll see how compatible you are. Just don't get side tracked. So if you are to break up with her at some point, make sure it's on good terms, and if you are going to have a fling, make sure you aren't going to be uncomfortable the next day about it. It all depends whether or not you're an akward-after night of sex guy.
-Kel