Had a Z4 2.5 (YES AUTOMATIC
) for 3 years before I got the 986S.
Great car, the run flat tires simply just
SUCK so avoid them at all costs if you decide to go with the BMW.
Driving wise, forget it the Boxster (especially the S) hands-down impresses the most.
The Z4 for me is a great looker, good performer and overall a good "cruise-in-style" vehicle compared to the classic looks and track-racing-inspired Boxster.
I am only 22 and I will tell you first hand that the BMW Z4 is the hottest car-toy to have now if that's what you are looking for. Top the free service with that and you got yourself a nice deal!
In fact, after my BoxsterS I am definitely leaning towards an MCoupe.