Yes it could just be that one in every few thousand were duds and the people who had them are the only ones bothering to go online and share their experience. In a few of the out of warranty cases it looks like BMW have given a 50% discount on replacement tranny which does kind of suggest that there's a manufacturing defect. Where people are reporting bad lurches but not total tranny failure they are telling them 'thats just how they drive'. I wonder whether many aftermarket warranties would cover this or whether they would class it as wear and tear.

Like you say it would be nice to have an insiders view, ideally a BMW mechanic.

Edit:

The TSB at the bottom of this forum is interesting, the TSB is for the 5/6-series but they apparently use the same gearbox.

This thread is also interesting, tallking about the same gearbox.