Did both...

1) I drove a '99 528i before the X5d for 10 yrs w/sport seats and loved it. No problems at all. But! they are different seats! And your 335 I bet has different seats too...

2) After my 50 mile/ 50 min drive of pain, which happened to be to the Tischer BMW dealership to pick up some parts I have asked them to let me sit in a '10 X5 w/comfort seats... they had one and gave me the keys. I spent about 15-20 min in it by myslef just playing around w/the seat and adjustments... and let me tell you - those things are bliss.... perfect adjustability, for my back at least - the upper backrest adjustment along w/the wide headrest felt just perfect. This was heaven after my ride from hell... I felt disgusting... and literally had tears in my eyes...

If you have any way at all... move planets to get the comfort seats.... BEFORE you get the car. Or at the very least make sure you sit in both for a solid while and make absolutely sure you know 100% that the sport seats are OK w/you before you agree to own them... or else you get a perfect car for $60k that you can't really use w/out swearing every time you get into it... that's the boat I am in anyway... In fact the discomfort for me causes me to repeatedly adjust my neck, back etc... to the point of distraction frequently... IOW, more risk on the road.

I don't know what to do w/this problem... it's almost like I feel caged. On one hand it is a perfect car, on the other its a ride of pain. If I could swing a $10k write off for now USED 2 month old '10 X5d trade in, I'd just re-order another one w/the comfort seats in a blink of an eye...

spacey