I started bike commuting again this year after a few year layoff. I ride 14 and 1/2 miles each way, at least three times a week, with a 12 pound backpack. I have worked my riding time down to about 54 minutes so I am averaging better than 15 MPH. I like to use the commute, (particularly the return trip), as a training ride. I am trying to get my ride time down to 45 to 50 minutes and, weather permitting, I plan to ride 4 to 5 times a week and maybe a longer ride on the weekend.
However, I am riding a road bike, not a beach cruiser.