ok, so the expert consensus is stop and go, city traffic, below 4500rpm for the 1st 1200 miles..

I'll add to that (and I did this on my MB).. change engine oil. The break in (by definition) will yield a lot of metal fragmentation in the oil.. I will pay the lousy $80 for new oil/filter for peace of mind. Then I will 1/2 the BMW recommended intervals for ALL fluids.