If you have ever driven anything like a Lotus Elise it has no PAS or even a brake servo you will appreciate that if you want a focused drive and want to be able to point the car in the perfect position/direction then you don't need it, even cars like 106 Rallye's etc don't have it and they are amazing, same with R5GTT's, on smallish cars under 900ishkgs its really not needed.
Conversely my integrale has it, 1300kgs, even has a cooler for the fluid for homologation purposes, but its almost like it doesn't, as it weighty and very very precise which can't be said for most PAS, the Sei PAS is just awful & I find most modern cars have have a terrible dead feeling on the straight ahead, and are to slow and not adjustable on speed. As for the adjustable type thats changes with speed, i think the fact the 'M' cars by BMW do not use it when the normal cars in the ranges do says it all for those systems, not up to it for real drivers cars.
As for they are easier to park, it will state in your manual not to just turn the car but treat as it has no PAS i.e. car is moving before turning steering wheel as you would with out PAS to make it easier on you, so make it easier on system, to do it while car is stationary put loads of stress on the system and wears out tyres very quickly.
Aaron.