Let me be the second. Serious cycling for transportation requires coexistence with cars, trucks and buses. It also requires always remembering what will happen in a confrontation with cars, trucks and buses.
The ignorant Gomers that yell "get on the sidewalk" are few and far between. Most motorists are rational enough to understand that if I wasn't next to you on the road on my bike, I'd be in front of you on the road in my car slowing down your commute. Why piss people off with idiotic stunts like this and turn them against you, when originally they barely noticed you?
No, the commute would be a lot faster. Drivers wouldn't be slowed down to 10mph because a biker is taking too much room and with on coming traffic you can't go around the obstacle. Traffic patterns at intersections would be better because you wouldn't have bikers running lights, or stop signs.
I asked a friend who is a biker why bikers don't follow the rules of the road at intersections. His response was, "because we would never get anywhere if we stopped with traffic". Every year there are 5-6 bikers killed in Chicago. It's not a good activity in a large urban environment. Bikers should go back to the suburbs.