Gonna chime in on the recent comments about Mike Miller's schedule. I used to be a huge proponent of that schedule and felt that BMW was sacrificing long-term owners (or owners of older BMWs) by switching to their "maintenance free!" schedule. And I'm a big oil analysis guy who watches closely the results.
While I don't believe the infrequent lubricant changes are good for the car, the fact is that we have plenty of high performance, high mileage, hard used BMWs now going on 10 years after the longer maintenance intervals were introduced. We are not observing a huge spike in failed engines, failed transmissions, or failed differentials. Cooling systems in the more recent BMWs are performing at the same rates as ones in the 90s and early 2000s were (which was not great, even with more frequent maintenance).
I have seen more BMWs with dirty engines, no doubt. But, for whatever it's worth, BMW seemed to hit the mark on less frequent maintenance - it didn't destroy their cars reliability.
I would not hesitate to own an Naturally aspirated BMW made in the last 10 years provided it passed a thorough pre-purchase inspection and showed signs of being well cared for (i.e. even treadwear, non-excessive suspension wear, smooth running engine and trans)
F80 m3 - 20k miles as of April 2015....08 535xit - 120k miles