Called the 1-800-FOR-MERC Customer Service Rep today and asked if he knew about the harmonic balancer problem. He said no and that all he had heard about was the power steering clamp problem on the ML's. I've got an appointment next Thursday for the dealer to check mine out before the warranty runs out. Think I'll have it done wheather or not its covered.
Like Sterling, I'd rather do it now than wait for a major problem when you least expect it. Just my 2 cents worth!