With my Surly Cross Check I've now got the speed and durability that I want for commuting. Most of my ride is on a well-kept, paved trail, but I ride on city streets and will use this bike for on/off road touring too. I estimate that, with my road components (Ultegra, 700x28 tires, improved geometry over my previous commuter-a mtb) I'm probably a good 10 to 20% more efficient. It's a fast commuter that feels just about as tough as my old hardtail mountain bike.