I thought the Madone 3.1 was pretty stiff too. The 5.2 seems even a little stiffer and a little more responsive. It was about 2 1/2 lbs lighter I believe. So that helps some. The extra carbon seat post etc... makes the ride a little nicer too. So yes, feels a little lighter on the road. I gained just over 1/2 mph on the 3.1 to 5.2 upgrade....then another 1/2 mph when I upgraded the wheels and lost another pound there. I went from my hard 10 mile training mile loop at 18.25 mph avg - to now all over 20mph avg in just over 1 month.

The the OP - take a look at Boyd, Williams, ROL to name a couple. I have the Boyd Vitesse in the 24x28 spokes. 1520 grams. Love them. If you're not going to be racing...just make sure not to go overboard with wheels.