I don't know if you have been watching the Rav4 boards. But it seems that their version of the Tesla drivetrain is suceptible to failure. The extended warranty is a highly recommended option.
I have not heard of any motor replacements for the BClass, so I thought that maybe they got our version right.
But then I started hearing a whining noise when accelerating. I took it in, and it turns out I need a new motor. My dealer gave me an E300, so I'm good for as long as they need it. I will miss being able to use the carpool lane for free.
If anyone else has experienced this issue, please chime in. Otherwise, I'll post the advisors comments when I get the car back.