My first thought Glam.
My brother has a BMW M5 and it holds the brake until you hit the accelerator, not until you lift off the brake pedal itself (which is fucking stupid as it renders the automatic parking brake function useless).
Anyhoo, day 2 with it and I find it's easy enough to throw it into Park at lights to save blinding the driver behind.
(Not a problem in daylight, but sitting behind someone with their foot on the brakes in winter, in shitty rain is mega annoying. I sometimes return the favour by firing the headlights into high beam and blinding them as much as they're doing to me.)
My brother in law's family are in the Taxi business and he says the Start/Stop function fucks the batteries, but most taxis only do local shit with lots of stopping and starting, which is possibly the point.
I think it's probably kidology tbh.
Does 45 minutes of idling emissions saved per day = the carbon footprint of producing and then recycling a car battery in a shortened lifecycle?
... then there's the blast of crap and stress on the engine as it starts.
I call Shite! on Start/Stop.
Probably saves you £20 per year in fuel, but does £200 worth of damage to the engine