I've been commuting on a cheap Gary Fisher bike for about 3 years now and am ready to make some upgrades. Since I really only ride on the street or paths, I don't need the knobby tires that are still on this bike. After shopping around a bit online I've started to eye the Continental Sport Contact Tires. What's everyones experience using these or any tire with little to no tread? Hopefully a tire like this will help me get a little more out of my bike without getting a whole new frame to start from (ie. can't afford it!).