We have it on current Boxster and it is very cooling on a hot day and works perfectly quietly.
Two years ago we went to Reims and it coincided with a heatwave of 38oC.
Had to have the roof up with aircon and ventilated seats on full blast !
Having said that I myself would not spec it on a new Macan at £639,
however my OH is insisting it is fitted so it will be on our options list. !!
We have it on our Macan - used it twice. Once to try it out and once to remind myself what it was like because it had been so long since I'd tried it out. It's a nice to have, but I wouldn't spec it personally.
Also had it on our old RR Sport - again, nice to have but literally never used it.