I noticed on the Trek 7500 FX ... I could feel the difference in the wheels when thiings started going fast.

Last night I rode a 5200 carbon fiber bike wiht fast wheels. Heavens!! Whoosh! Those miles just flew by! Funny thing was there were only three of us on the ride and one of the guys had ridden his "grandpa" bike (7500FX but 32 tires, even if they are slick). So I was sort of accelerating away from myself sometimes It didn't even really fit me (not my bike, but its owner's legs are roughly the same as mine) ... the power tap was fun to watch, too. So even tho' it looks like Trek *hasn't* picked me, I got to try out the fancy gear