Hi all,
In my opinion the Diff failure issue is not limited to a particular model or part number, it appears that diff failure is common (some may disagree) in some BMW cars built between 2007-2009. Most diff part numbers in that period are marked as superseded in the BMW inventory. Whether it is a poor metal composition or bad design, the problem is there.
As far as my car goes, I don't plan to replace it just because of the diff failing. There is a lot to like in BMWs.