70 is about as fast as I like to go. Once I get away from the city I might push it a little further. It depends on the situation I guess. Being an ex-street racer I discovered that it wasn't really speed that got my adrenaline going, but acceleration.
but i ENJOY the ride at around 50mph thats when i'm grinning like a possum!
I just try to stay about 5 to 10 above the speed limit or whatever speed keeps me from obviously being faster than everyone else and thus attracting the attention of the law. A lot depends on road conditions, the "personality" of surrounding traffic, atmospheric/lighting conditions, etc. For me, I guess there's no simple answer to your question.