Saturday I road my Gary Fisher Tiburon 27 miles with 7 miles on some rough hills. I averaged 13.75 mph. I didn't think that was to bad for a hybrid bike. Yes the upright sitting position does increase drag, but I am doing well. I am not trying to go far, but I do get a good workout. I am down to 306Lbs now, and I notice I have a lot more wind than I did 2 months ago.
Mark
The more you ride the better you feel, the better you feel the more you ride.