I've done it a couple of times, I think.
It's very problematic.
D&D rules, first off, don't describe reality all that well. When you're imagining people running about with swords, riding horses and slaying dragons, it's all well and good, since that's a long way from what most of us experience as reality anyway. The fact that the rules don't really mirror how things might ACTUALLY work isn't a problem. It becomes much harder to suspend one's disbelief when the world being simulated is so familiar to you. Why is it that a 15th-level character can survive just about anything anybody in the modern world might do to him?
Aside from the rules, it can just be hard to maintain disbelief (or belief, if you like) when dealing with things you're so familiar with. It's hard to avoid a fair degree of self-consciousness.
Finally, it's much harder for players to resist the tempation to argue with the DM about what is or isn't true. Is there really a Seven-Eleven on the corner of 5th and Main? How long does it take the firemen to get there? These are issues your players will feel much more informed on than similar details in your campaign setting, and they may feel compelled to point these things out to you -- which brings play to a screeching halt, most times.
But I'm not the greatest DM by any stretch, and it was long ago. You may have a lot of fun with it.
