I was always the youngest girl in class, and it was never an issue. I wasn't in public school by the pre-teen years, but I could definitely see the benefits of not being the first girl to hit puberty.....now for boys on the other hand, being one of the last ones to hit your growth spurt? Probably not much fun - especially if they want to be involved in sports. The worst part of being that young actually goes back to Bret's point. I couldn't go out to the bars until senior year, whereas most of my friends where out Jr. year as well.
Yep, I think you nailed it. No girl WANTS to be the first one with boobs, but being the first guy with a beard is sort of a cool symbol. It's not a big deal for a girl to bum rides from her friends, but for boys some see it as a little emasculating. I can definitely see where it would suck in college, though - I was a winter birthday, so there was really zero question for me.