I thought I'd just post up about my experiences with PS4S on the M3.
I've done about 30,000 miles on the rears and they are down to 3mm so nearing needing replacement however the performance and grip they offer, even in these cold/wet conditions we have is still incredible. Even with such low tread you really have to provoke the car for it to get out of shape, and honestly that was the case when the tyres were brand new anyway. This was very much NOT the case with the Continental Sport Contact 5P that came with the car when I bought it (the combination of M3 power/torque + lower tread was borderline lethal with them!), and also the OEM fitment PSS definitely had a notable performance drop-off at lower tread depths in these conditions.
With lockdowns and everything causing my annual mileage to tumble from ~25,000 / year to ~5,000 year I've still got a good few months of life in them, especially as we'll tend to use my wife's Evoque more this time of year anyway.
I know there are comparably good offerings now especially from the likes of Bridgestone but with the great experience I've had with the PS4S, coupled with the fact that I know they last REALLY well, means that when I replace them it will be with another set of PS4S.
Front tyres faired less well needing replacement at ~25,000 milee (still good mind you) because the very inner shoulder had worn through owing to the tracking being slightly out, plus the M3 runs from fairly aggressive negative camber for a road car. Middle and outer were still at 4mm
All in all I'd give PS4S 10/10.
(Front tyres are 255/35/19, rear are 275/35/19).