I ride my Tomos at 40+ most of the time, and everything seems to be holding
together fine, although I do expect premature brake wear.
I think it is even more fun, being able to pass a car when you want to. Nothing
tells somebody they are driving too slow, quite as much as being passed on the
highway by a moped. The looks of astonishment are worth every penny I've put
into my bike. This isn't to say I don't also enjoy the leisurely rides as well. Your
comment about being able to stop and say "hi" is well taken. I put about 50 miles
on my bike last weekend, and during the course of the day ran into (not literally)
three old friends during the day. One took the bike for a quick spin, and now I'll
be taking him to where I got mine this weekend.
Going slow is great, going fast is just a little better :-)