Averaged under 10km/h for a 9km ride on the weekend. Excuse is I was riding alongside my five year old son on the way out, and towing him on the way back, and we had to wait for my 3 year old on the other bike (towed behind my wife's).
Commuting for me is 12.5km each way, a bit more since they started building the Perth arena thing. A nice distance for daily commuting for me. I used to live 5km from work which was a bit too short. Before that it was 25km which was good exercise but I didn't keep it up every day. At the moment I ride pretty much every day unless its raining when its time to leave home, or I need to exercise my motorbike (needs to be ridden every 2 weeks or so to start well).
