I am asking this question for a good friend who is a currently previous series M5 owner and is ready to get a E39 M5.

Is there a list of known issues to look out for in the E39 version? He is not a Roadfly user so he has not yet taken the steps here to ask about issues that he should know about as he shops for a car.
If there is a topic in the archives that covers a M5 buyers checklist you can direct me to, that would be super.

Mike (2001 M Roadster)