I used to time my commutes, back in my first year of cycle-commuting (I'm now on my third). It was fun then, watching the improvement. But after a while, I stopped improving, so I stopped timing myself. Occasionally if I'm feeling energetic, I'll still check my watch at the start and finish. I still generally push myself to ride as fast as reasonable, 'cause I like going fast, but I don't concern myself with how long it takes me anymore.

I've never used a cycle computer on my actual commute, so I don't know my best actual commuting moving average speed. The fastest door-to-door time (including stops) for my 9.6 mile commute that I'm aware of is about 35 minutes, giving me an average overall speed of 16.5 mph. Today, I pushed myself harder than I ever have on a commute, under much more ideal conditions and on an overall faster route.

Today was really just a fun experiment: Is it possible to maintain an average moving speed of 20 mph in an urban setting? The answer, as far as my abilities are concerned, is still no.