For "nail in the tire reasons", my wife and I switched cars (I drove her ML320 that had a nail in the tire and she drove my C230WZMT).

While she was driving, she heard some pretty loud noises, but didn't think it was our car, mainly cuz this car's only about 6 months old. Then she noticed that the air conditioner shut off by itself.

To make a long story short, in the words of the MB service advisor, the air compressor blew and it was like a grenade, sending pieces of stuff everywhere. For instance, if you turn the car on and hit the accelerator, it just sounds like tiny pieces of schrapnel being blown all over the place. Apparently, this is the 3rd one in 6 months that he's seen. But he said that this only happens on the 4-cylinders, not on any of the V-6's? Why would that be? Is the air compressor for the AC mounted differently in the 2 cars?

Are you talking about the air conditioning compressor, or the supercharger? Supercharger failures are fairly common. On car in CA has had its supercharger replaced five times. That is an extreme case.

It was the AC compressor. He said that they were going to replace the entire air conditioning system (I assume AC compressor, freon, etc.) and I'd get the car back by Tuesday or Wednesday of next week. I thought that was pretty good considering that it was towed into the dealership late Thursday night.

So for now, we're a 2 ML family - they gave us a black ML320 for a loaner...