The light sensor does work to turn the brightness up or down, but is claimed to turn off the power when the cap is put on.
The light never turns out in total darkness, even after several hours. It also will not turn off when the sensor is covered with two layers of black electric tape. Drains battery in a month or so.
Pros: small, cheap, looks nice
Cons: hard to zero, green dot does not go out in darkness, drains battery anyway
This review was written in the old system and had content requirements that are different than reviews written today.