I strive to maintain a constant speed, so the gap in front naturally gets larger as traffic ahead speeds up. Back in the day, when I was typically in a hurry and driving insanely, I liked large gaps because I could slalom through them at high relative speed. I don't do that anymore. I hate it when bikers blow through at 100 kmph relative speed. But at least they're small.

Edit: I also hate it when bicyclists blow through city traffic at 10-20 kmph relative speed. For some reason, I'm more afraid of accidentally hurting them.