rear view

I may be missing something obvious, but does anybody know what the power button on the rear view mirror does? Initially, I thought it may be something to do with dimming headlight reflections, but with the tinted windows at the back, I can't see any difference. As far as I can tell, it just...

We all know how the rear visibility is poor because the spoiler (or whatever you call it) sits right in the middle of where you want to see. After six months of ownership I've just found out something which improves things quite a bit and thought I should share it in case, like me you didn't...