On the way to work (9.5 miles) I average 17.5 mph. On the way home it is around 14.2 mph. Uphill on the way home, obviously.

By the way, I just bought a jacket from Performance last week, and really saw a slow down at high speeds. Talk about wind resistance, and this is just a thin shell, in my size! Places where I can go 30 mph with a jersey and armwarmers are near 26-27 with the jacket!