Well I just switched out my bike's original Vittoria Zaffiro wire-bead 26 TPI tires for some Conti GP 4-season tires with 430 TPI.

I don't have enough miles on them yet to really tell, as I've only done one real ride with them since I switched, but that ride was one of my fastest average moving speeds to date.

I'll know more after a couple of weeks of 30-mile round trip commutes if they really make much difference or not. They are saving me 280 grams total rotational weight from the old tires.