Elsewhere, crasic writes:
The Most Direct Route is Not Always the Best
... Your driving commute route is usually a horrible bicycling commute route. I purposefully avoid big roads as much as possible and take small residential streets or dedicated bike paths when available. An extra mile on a bike path can actually save you time over a shorter busy commute route — not to mention the savings to your health, safety, and the increase in your general enjoyment. If my commute reminds me of my Sunday ride, then I know I have a good route.
You are a bicyclist. There is no reason to endanger your life on the 50mph [80 km/h] express-way when the 25mph [40 km/h] residential street can get you there just as quickly. In California, residential streets are often extremely wide (Parked car + Bike Lane + 1.5Width lanes both ways) compared to dedicated expressways — and can be orders of magnitude more safe and comfortable to ride. The pavement is often newer and less broken.
If you are new to the area, spend a weekend or two just exploring local residential streets. Hop on over to Google Maps and find the a way to use small streets to get to where you need to go. (Often this involves riding through the residential maze and with at least 5 or 6 street changes.) Practice your route at least once and carry a printout of the route with you at least the first few times.
[...] During busy commutes, drivers are often distracted in many different ways (putting on makeup, drinking coffee, worrying about being late, etc.) and can be unaware of bicyclists. Nothing will ruin your day more than an accident on the way to work.
John Forester's view
But, if I remember correctly, John Forester writes in Effective Cycling that four-lane main streets (with traffic lights) are better for commuting than little two-lane residential streets (with four-way stop signs at every block). The main streets are straighter and flatter. He adds that, if you take the lane, drivers will notice you and give you space. (Personally, I do generally take the lane.)
My usual practice
[Edit: I'm in Toronto, Canada.]
I'm seriously annoyed by having to brake heavily at every single four-way stop sign (especially when descending). Also, the residential street grid doesn't always pass underneath expressways or major railway lines. So I tend to end up doing most of my commuting along busy 30 mph [50 km/h] main streets, rather than quiet residential streets.
I don't usually commute during rush hour. The car drivers seem to calmly accept it when I take the lane; and I accept the drivers' right to use the road too.
Is it wise for me to stick to main streets for the majority of my ride, even though there are quiet residential streets just a block away?