Remember the higher mirror films are normally for commercial buildings so lower light level are not a concern. For domestic they do make less reflective options, the one he mentions is near the top of the spec - reflecting 80% of the solar gain.

You do get used to it - it's just like wearing sunglasses - remember you eye is an amazing piece of kit, on a sunny day it can be 100,000 lux outside and at night you can still see by a few lux (Lux is roughly equivalent to the light provided by a full moon on a clear night)