I don't have the car yet, but I'll give you my perspective if it helps any.
One reason I wouldn't want PASM is because it's just another gizmo that could potentially break-down. While I know there are benefits, just like TPMS, I question the validity of it in the long-term for its cost justification to fix it.
On a side-note, I wanted the PCM Nav as well, but figured to omit it after thinking about how future systems can be a greater benefit. Obsolescence prevented me from wanting built-in nav.
Future Cayman S: 56 - Cobalt blue, RA - Cocoa leather, M6C - floor mats, 639 - Sport Chrono, 460 - sport leather steering wheel, 403 - 19" Carrera S wheels, P12 - dimming mirrors and rain sensor, P74 - bi-xenons, 342 - heated seats.