My experience is that with ridiculously much exercise, I can do with less sleep and still feel excellent.
However, that usually means trading one hour of sleep for one hour of additional exercise. And I'm lazy, so sleep it is! :-)
The thing I'm jealous at you US people for most of all (except those from Maine and Alaska) is the ability to wake up with the sun each morning. Here in Northern Europe, the seasonal differences are simply too large.