Light Reactive Insert, di they work?

I find it annoying to have to stop and put sunglasses on if and when the sun decides to show (like today).
and not sure if i would like a permanent tinted insert… or even worse keep changing it with a clear one.!

so do the light Reactive Inserts work???

when i say work i mean:

are they worth the extra money
how quiclky to the darken return to clear,
what happens if it is overcast? is it dark - or clear?
any other comments