When I used to hit 30, slam it to near 0, 30 again, 0... my garmin showed a chart of my commute that ended up looking more like a seismic chart during an earth quake. Now with my fixie, I get to work in just about the same amount of time but it feels easier on my body and since I'm afraid to use my front brake, I end up using my legs to slow myself down. I'd skip or skid when I need to slow down really fast but to preserve my joints and tires, I end up just taking it easy from light to light. It's only 2-3 minutes slower than my road bike on my commute.