What I can tell you is that my 2006 330i with 135,000 on the ticker is aging quite well. The car is simply put together very very well, and it's a jack of all trades- decent gas mpg, fun to drive every day (after all these years), fun at the track, and reliable.
My aunt's e34 528i sport (black/tan leather, 5 sp drool...) had 260,000 miles when she sold it. Great car that didn't see cca type maintenance! haha..
I wouldn't expect the new cars to hold up any worse, but like all BMWs they will have their weak spots- direct inj which will require walnut shell blasting every 60k or whatever, and a whole slew of elec gizmos that will be pricey to fix. That's why when I got my e90 I wanted as few options as possible... I didn't want to shell out $$$$ to fix a navigation system years down the line that I never wanted or needed in the first place. Same goes for ridiculous gimmicks like park distance sensors and back up monitors... really??! It's not a large vehicle.
I'd love to drive a new 328i M sport with a stick, fortunately my dealer hasn't stocked one yet. I'm sure if I took it for a ride I would be an owner.. after all the feel of the wheel makes the deal