Let me comment that the ride on the Z4 is not harsh. It is not Lexus-like either. I've been driving a Porsche Boxster for the past 27 months and am saying good-bye partly because of the hard ride. The Z4 is definitely a solid ride and holds the twisties with plenty of throttle quite well. My Melbourne Red 35i just made it across the pond and is due at my dealer in a couple of weeks - am very much looking forward to the "trade"!
And do get the sport package - the Z4 suspension is NOT affected by this option, but you get the much more comfy and adjustable seats with this choice.. along with sharper looking wheels, etc.
I'll be 62 this year and have a growing low back problem that is not happy with P-car drives, but the Z4 (I've done much driving in one) is much, much less harsh.
The only other concern is the very modest amount of trunk space. Lots of threads on that one - and a couple of soft duffle-like bags will work, but just be aware of that. As far as the 180-mile distance to the dealership.... just have it put in writing that they will not only offer you a loaner if service is needed, but see about having them sweeten the deal because of your inconvenience should you need to get back there other than the once/year free maintenance visits.
Oh - and that oversize pic below is me picking up my 2011 e91 at the Performance Center Delivery last year - If you order your Z4, you might want to do that too... it is a significant blast and an experience you won't forget.
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