On my way in today, I hit 38.2mph. And that was while I was also riding with both of my shopping-bag panniers on the back.
Total time: 17mins, 53secs
Total distance: 3.95 miles
Average speed: 13.3 mph
Total calories: 1067 Cal
Fastest speed: 38.2 mph (!!!)
Average heart rate: not recorded
I'm quite happy with that accomplishment, and am also amazed at the estimated caloric burn of 1067Cal (which is roughly double of what I supposedly burned in total yesterday in riding to campus, then to Trader Joes, and then back home - a total of 14 miles, but at a much slower speed than this morning's blast into town).