Eeehhh.... Yes. I have. And we ended up dating.... for about 6 months. Actually, he fell for me - and pursued me, more then the other way around.
I had alot of fun, and it was INCREDIBLY convenient - because we had all of the same friends!! We were into the same things and got along very well.... Unfornuately, in the end - things didn't work out and the break-up part ended up being THAT much messier because we were very good friends beforehand....
Since we had all of the same friends, we couldn't hang out as a collective "group" anymore, without somebody being weird about it. I was getting ready to graduate from college and he still had a year left... so in the end, I basically severed ties from all the "friends" I had in that circle, and started gravitiating towards other circles of friends I had....
It all worked out okay, and I don't know that I would change a thing - because I had the most fun with my BFBF (best friend boy friend), then I'd had with any person I've dated. It's just sad, because if you already "like" the person, you're probably more likely to fall in love quickly.... so I think that is kinda of what happened with us. Even though I dated a lots of people beforehand, and a few of them were more long term relationships (which means more then a year for me), then my BFBF... I really feel like he was my first LOVE... like intense, crazy.... first love. However, we knew so much about either other before we dated, our relationship felt like it was moving at light speed. So, its kind of sad........
Anyhow. I don't want to be a downer - because I'm sure people have success stories too!! If it works out, it could be the perfect combination, since you know you already get along really well!! I just didn't really have a good experience with dating a person that I was good friends with beforehand...