Seems relevant, since some hybrids are fairly upright riding positions compared with road bikes. I've lowered the bar a bit on mine but it is what it is and won't get much faster.

I was kinda curious myself and began using Cyclemeter a few weeks ago. It's probably not quite as accurate as a calibrated speedo on the bike, but over the long haul of hundreds of miles it shows my average speed for 10-30 mile rides has gradually increased from 12 to 13 mph. That's probably as good as it'll get with my comfort hybrid, which is pushing 35 lbs as I usually ride it, with heavy puncture resistant tires, water bottle, a few tools and first aid kit, usually a compact camera.

What surprised me wasn't a small improvement in average speed, but a more significant increase in speed on some difficult sections that used to give me fits: some hilly climbs that I used to granny gear, I can now take faster; and some long downhill runs that I used to take in a middling gear at 18-20 mph I'm now riding close to 30 mph. But I'm close to spinning out near 30 mph and can't quite seem to break that barrier. And my upright riding position is like a parachute above 25 mph.

I don't dwell on speed but it's interesting to get a little objective data in addition to mostly relying on how I feel on any given day.