I decided to try the Take a Look mirror. I got the regular and compact to try on my (prescription) glasses. Mounting is simple - I did bent it ever so slightly for a somewhat tighter grip to my glasses frame. Flipped it down and to the left (U.S. right side riding), put on my cap, helmet and made some micro adjustments so I could just see the edge of my helmet.

So far I've used it twice; yesterday and today, morning riding (after the low sun angle that blinds drivers during my westward uphill leg is about gone).

My ride is almost like a crit; square block - starts out eastward uphill, turn right / south - flat, turn right west - flat, turn right north - downhill, and right east again. All legs are bike lanes.

I've found the point where if I'm looking ahead I can turn left slightly, about 10 degrees, I can keep that head position and turn my eyes 10 deg right to see forward and turn my eyes again 10 deg left to see the cars coming up behind me on the left (and on the right, during some parts of the ride). I can even see further back when they change lanes over one when they see my lights. I'm always looking for their lane position and many are on the far left side to give me room. It was windy today, so I could see (and not hear) them roll over the lane marker bumps a few inches to give me room.

I get a steady picture of what's behind me with no shaking so far on the 2 rides. Kind of windy today (15-20 mph / 24.1 - 32.2 KPH) - mirror still steady.

One thing to note is where the sun is so you don't reflect it into your eyeballs.

I've found the head position and 10 deg slight turn to the left works on the tops, hoods, and drops. I kind of force myself into the drops during the downhill to keep flexibility, so I know it works in this position.

eta: After 5 days amazon didn't ship, so I complained. They upgraded shipping to overnight. The compact is just too small, so I requested a refund. They said refund initiated, keep the compact!