I have an ST1 LTD. With >900 feet of steep ascent in my daily commute, i'm only averaging 16.5-17 mph through the city. So, there are lots of stop lights & traffic. Sure, I get to fly 35+mph down hill, but that's a limited amount of time compared to the lengthy & slow climbs I have to do. On my regular bike, I was barely able to avg. 12mph, more likely 10mph on those commutes. So, it doesn't necessarily seem like a significant change, but it sure feels that way to me. This works out to a 33-70% change in avg. speed. Commute times are now under an hour compared to the 1.5 hrs on the regular bike. So that's about a 33% reduction in commute time.