The weather stripping on one door kept falling down.
The door locks went into ghost mode frequently requiring 3 visits to the dealership to correct.
The drivers side power window failed in the lowered position. Good thing I had a garage.
I had a mysterious ear-splitting grinding noise from one of the wheels/brakes. It appeared to be something came loose and it would start when I made a left hand turn. I could make it go away with a right hand turn. So I travelled home making right turns only for 25 miles. I took it to the dealer immediately, who found no problem, but it mysteriously went away.
I purchased this car as a replacement for a mini-van (which my wife felt quite frumpy driving). I thought I was doing a good thing by buying her a "quality" Mercedes Benz. I've owned mostly Toyota vehicles. Very good quality, but sometimes missing in the personality aspect.
I also purchased the 3rd row seat. This was one of the reasons for purchasing the ML320. The dealer was not help in telling me that the 3rd row seat was a permanent fixture that could not be removed. I discovered after having it installed that the seats were removable.
I must comment on the dealership. Here in Phoenix, Arizona there were only two, now three. I hated the place, I spent the extra money to purchase an ML320 and felt like a leper waiting in the service line watching the Service Managers fawn over customers in 80K+ cars and leaving the "many" M-class customers waiting.
I happened to also own a Lexus RX300 at the same time. Which I can't say enough good things about, including the dealership/services.
The kicker is that when I finally got tired of the ML320 and I tried to sell it, I almost had to give it away. Comparing the Mercedes resell and Lexus, ML320 vs. RX300. Two years after purchase at similar prices, the ML320 was worth $10K less.
The only upside to the ML320, was the engine and transmission felt smooth and powerful. The ML320 also had a much better turning radius that the R300.