Depends on the hill. Extremely long and steep, I'll usually coast. But if it's your run-of-the-mill downhill I'll keep pedaling, however I usually won't increase my pedal pressure. I'm not looking to add additional speed as much as just keep my cadence going. Then at the bottom of the hill I can gradually increase the pedal pressure to keep my speed from dropping off as quick.

The biggest hill on my commute would probably let me hit 45 mph if I really gave it a go. Unfortunately it ends at a "T" intersection with a very busy street and a stop sign. So I coast down that one because there's really no benefit to me adding additional speed that I'll just have to scrub off with the brakes.