As I recall (or at least seem to at the moment) from my model rocketry days as a geek kid, a eliptically rounded leading edge is usually considered to be the most aerodynamic. Putting a wedge on the front of the head tube might do a little, but I think it's more for looks than anything else. I mean, if you were marketing an absurdly priced frame under the model name of "Blade," you'd want it to look sharp, wouldn't you? Nobody is about to market a Ti frame under the name "Butter Knife" after all.