Quoted thread is nice to see but has no useful information. Here's a list of my thoughts:

1. it's more dangerous to ride without a mirror than with one. It's better to be prepared for that traffic rush.

2. helmet mirrors help a bit if you can get used to them
2.1 They will never be very good for right eye dominant riders. They only give a hint of vehicles.
2.2 You don't look in the mirror, you adjust the mirror for most situations and move your head to see behind
2.3 details are very difficult to see in them
2.4 looking too hard in mirror can lead to unexpected results as riding into a hole

3. road bar end mirrors will not work at all if you reserve that spot for flash back type of handlebar safety lights

4. best solution? unknown, but here is what I plan to try:
4.1 keep on using the helmet mirror as a second mirror
4.2 I'm going to put on a handlebar mirror and see how that works out. Right now I'm looking at this
http://www.rei.com/product/47846426.htm? and planning to put on left side of handlebar, or on handlebar extender.