They're fantastic. At no point will a car be beside me where I cannot either see it with A.) my eyes B.) the standard mirror or C.) the blind spot mirror.
When adjusted properly, you can do this with normal mirrors like on my 2010, no blind spot thingy needed.
Remember when adjusting mirrors, you do not need to see the side of your car, you know it is there, it is not going anywhere. You need to be able to see everything else, either in the side mirror, center mirror, or directly with your eyes.
<sorry if I am being repetitive, did not read page 2 of this thread>