I just picked up the same tires, but I went with Continental Race inner tubes (butyl) instead of latex. I haven't had a chance to really ride them long distance yet, but I have taken a few laps around the parking lot of my apartment complex. It's hard for me to tell a difference at this point, because I installed them on some Reynolds carbon clinchers that had just returned from the LBS (I was having them trued). My previous ride a few days before was on Fulcrum 7 wheels with Vittoria Rubino Pro Slick 23c tires.

If I had to directly compare my short ride in the parking lot (more like several laps and a few sprints) with the Conti/Reynolds wheels with the longer ride on the Fulcrum/Vittoria combo, I would have to say the Conti/Reynolds setup felt more "sluggish." I'm 190#, 5'11" and ran the pressure the same with both wheelsets (110 rear, 105 front). I think the carbon fiber rims are to blame for the way the wheels felt and not the actual tires. I was surprised by the huge difference in road feel after going directly from a heavy and stiff aluminum rim to an ultra lightweight carbon clincher rim. I'm definitely not claiming the Fulcrum 7s are faster than the Reynolds mv32c ul, but shallow carbon fiber wheels just kill all the road feel which makes them feel sluggish.

Anyways, back on topic...

In order to really see how these Conti gp4ks perform, I think I need to put them on a set of aluminum wheels. I also need to run them back to back with another tire like the Rubino pro slick 23c to see if there is a noticeable difference. In other words, I need to keep everything including the wheels constant so the only variable is the tires. I'm thinking two 50 mile rides over two Sundays, different tires each time. It will be interesting to see how my performance numbers come out.