To the 15th of October commenter, there's no need to get ultra defensive of the Mercedes M-Class. The original poster just had a bad experience with theirs and it's their opinion. The fragile water based paint on the M-Class is a known problem and complaints of paint chips all over are common on this and other real world owner review sites.
The first commenter on here obviously does not own a Mercedes. They are probably one of those dreamers. If you own a ML320, ML430, or ML500 you would know the problems they have. The main problems are the brake pads, electrical, and paint. I unfortunately bought a ML320 for my wife which was great until around 30,000 miles. Several times she called me at work saying the car was running very rough and the transmission was shifting with a clunk. Mercedes of course found nothing and said it was fine, but it happened again within month. The Mercedes dealer service is horrible. I tried 3 different dealers in the LA area and all were the same, snobby. In early 2004 I bought her the Lexus RX330. Buying this was such a relief. From the second we arrived at Lexus they treated us with respect, like we were their only customer although every salesman in the dealership was busy with a customer. Unlike Mercedes, Lexus service is amazing. They give you a loaner car for the simplest thing like an oil change. Lexus I now see why you're the number one luxury car in the US.
DId you service the Transmission at 30,000 miles like you were supposed to???
Transmission guy told me once that the main reasons transmissions fail is due to owners lack of maintenance. I don't know why people think a car does not need maintenance.
After working with advanced drive train teams in (near) Detroit for the last 25 years, there is one thing I have learned about well built automatic transmissions. Leave them alone! At most they may need a transmission fluid change every 100k miles. Transmission shops like AAMCO are to be avoided at all costs. The only time a dealer will recommend transmission service is when they have a known bad model design, and then this rotten tactic is used to shift blame onto the customer.
Automatic transmission fluid is in itself a cleaning agent. When failures occur before 200k miles, it is always the fault of the design. A well designed automatic transmission is an amazing work of art. Unlike with engine oil, a transmission operates within an uncontaminated environment. It simply does not have to be changed as does engine oil. Fraying internal gaskets are the only possible contaminate within a properly designed A-T. And even this is a very rare problem. Good A-Ts are wonderfully long lasting.
The poster that has been led to believe that a transmission needs service at 30,000 miles is just the kind of customer dealers love. Those dealers who are selling garbage, and who need an excuse to hide behind.
I myself have given up on GM and Mercedes. Give me a 4EAT any day of the week, regardless of what car it is in. Or a mid 1990s LS400 Lexus. I can't waste emotion on 2nd rate "luxury cars" any more, when other top of the line cars are available at low cost. Life is too short. I love luxury cars that don't leave me high and dry, or with costly repairs before their time. And there are plenty of them out there.