Originally Posted by dhk2
I rely on mine all the time without looking over my shoulder. In fact, I get a much clearer and longer view from my helmet-mounted mirror than I ever would by a quick glance relying on peripheral vision. Same when I'm driving the car: I rely on all three mirrors when changing lanes, and virtually never look back which would require taking my eyes off the road for a longer period of time. Mirrors are required on modern cars because they are the only way to drive safely in traffic on multi-lane roads, not because they are some kind of crutch for beginners.
My though is that anyone interested in really "paying attention" on a bike should use a mirror. A few of my riding buddies still don't use them, and they say it's because they really don't need to pay attention to what's coming from behind. Their opinion is that it's the drivers obligation to keep clear when passing, and if they fail to do that, there's nothing the cyclist can do anyway....you're going to be hit. In other words, using a mirror to constantly check and call out "car back", or "car passing" is a useless act, because a cyclist can't leave the traffic lane fast enough to avoid being hit anyway. I admit that argument (for not using a mirror) may be valid, but for me the clear view back gives a sense of security that I wouldn't have otherwise.