Personally, the only thing it would really change is how quickly I decided we were sexually compatible.
I've had 2 reasonably long term girl friends, one of them I slept with on the second night we met up (note: we started DATING after this) and one where we slept together after about 2 months. The first relationship lasted longer, and it never even really entered my mind that she was 'easy' or a 'slag' or whatever other insults internet warriors want to say. It later turned out that I was actually her first, which I did think was a bit weird, but she basically explained it away as her knowing that I was the right guy, which I guess I kind of was since we were together for nearly a year.
Second girl we were together for about another 2 months after that. The relationship broke down for other reasons, but again, I was her first and although it was the same with the first girl, we didn't have that 'spark', if you get me. Personally, it wouldn't affect my opinion of them at all, and, like I've said, if anything (assuming I knew the girl at least somewhat well beforehand, i.e, mutual friends etc) it would probably lead to the development of a relationship sooner than if not.
We're young and care-free. Trying before you buy is important.