personally, I value efficiency (commute about 200 miles/week, energy savings are important). So I ride a super light (15 lbs) aero road bike with aerobars, and carry the bare minimum in a backpack or aero seatpost bag to reduce drag. I usually average 20-22 mph over my 40 mile round trip commute...My whole set-up is actually ironman bike-ready (for which I am training).

My weight: 125 lbs
Bike weight: 15 lbs
Weight of gear+water: 10-15 lbs depending