Here's the thing that cinched it for me (HUGE) (archive)

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apologies to Bimmer Magazine for any mis-typed bits, and remember that it was written in December, 2000 (when they talk about what engines BMW recommends have a break-in service).

Question: I am on the waiting list to buy a 2001 BMW 330i with Sport Package. I want to know a good way to break-in the new engine. Do I need to change the oil after 1,000 miles? What about the transmission and differential lubricants. I was about to buy a 328i, but I decided to wait for a 330i with the bigger engine after reading your magazine. (some guy in Edinburg, Texas)

Answer: The break-in driving instructions for your new 330i will be on a sticker affixed to the inside of the windshield. As far as changing lubricants for break-in is concerned, the answer is that it depends upon whom you believe. According to BMW, there is no need to change lubricants for break-in any more (with the exception of the E39 M5). Engine oil is good for 15,000 miles, and there is no need to change gearbox, transmission, or differential oil--ever. To our knowledge, BMW has never explained this in any mechanically-cogent way.
If you believe the BMW enthusiasts and technicians of the world, on the other hand, you'll change your driveline fluids for break-in at about 1,000 miles just like we always did, followed by gearbox and differential oil changes about every 30,000 miles.
For many of us, BMW's extended engine oil drain intervals, never-needs-to-be-changed driveline lubricants, and no-need-for-a-break-in-service all arrived a little too closely on the heels of free scheduled maintenance to be taken seriously - especially in the absence of that mechanically cogent explanation. Whether BMW's new maintenance-free service recommendations are good advice or merely some sort of marketing hype or cost saving measure remains to be seen. (Back when customers paid for their own maintenance, the dealer's position was that you couldn't change your driveline fluids often enough.) These cars haven't yet reached mileages where a lack of lubricant changes is going to show up in the form of prematurely worn out driveline components. It's too soon to say for sure, but we know how we're betting.
That said, whether it will make a difference depends on how long you plan to keep your car. The fruits of good lubricant maintenance show up over the long haul. It's the difference between a 90,000-mile component and a 250,000+ mile component. Regardless, we're confident that BMW's service recommendations will, at a minimum, see drivetrain components through the warranty period, and probably through the lion's share of 100,000 miles.

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