That never sounds like a good plan. No, I haven't. Actually, I tend to be the logical (and dateless) voice in the wilderness shouting out the evils of letting professionalism fall by the wayside over emotionalism.
Ask out the cute Barista who served you Starbucks for the last 2 years; she might say yes. If she says "no", however, you have just earned a lingering awkwardness that will interfere with all future trips to your favorite coffee joint. Weigh it in the balance; there's a 50/50 chance that it will go either way. Maybe it would be better just to keep it professional at the coffee counter and wait for a less dangerous opportunity.
The above is, however, kind of small potatoes compared to your job. After all, you can always ignore the Barista in the future or visit another coffee shop; but you can't ignore your boss, and finding another job is not a fun way to wind up having to deal with something gone wrongly.
I'm writing this from the perspective of a (possibly overly conservative) male. Nevertheless, I believe that my philosophy is equally valid without regard to gender. The workplace is for getting the job done; anything beyond that leaps into risky territory. Sure, I'm no expert; but if it were my choice, I would definitely back away.
Ultimately, you've got to figure out what you define as "acceptable loss". Keep in mind that the workplace is already irritating, challenging, and often strangely dramatic under neutral conditions.
Here is another unique thought to help you formulate an opinion: What is, would you estimate, (based on your present knowledge) the chance (in percentage) that a relationship (as proposed) with the individual in question will end with a happy lifelong marriage? "Are you crazy?" is probably your response to this question. Indeed, you probably aren't yet sure if this person is good date material, much less marriage material; and so, assuming that the suggested relationship is probably (at minimum) 75% likely to eventually end, what is the chance that it could end without impacting your career?