I was initially disappointed with the rear view provided by the stock mirrors. But then I spent some time playing around with how they are aimed. If you tilt the mirrors inwards quite a bit, so that a good chunk of each shoulder is visible, the view out the back becomes excellent. The field of view of the two mirrors ends up overlapping, so you can see directly behind you with either mirror. The stock mirrors are slightly convex, so the outboard edge of each mirror provides a big field of view. So even though your shoulders are blocking ~20% of each mirror's field, the overall view is optimized.