HMMM your all scaring me now. I just brought a 2007 GS 350 off lease. Funny thing is that no one every deleted the phone book so today when I bonded my phone I saw all the old numbers. I was tempted to call the previous owners home number and see how they liked the car, but I found this forum so no need to freak them out like that!!!!
Anyway I just got rid of a 2006 A4 2.0T. It was fun, has a great german ride for sure. But the issues were killing me!!! I cruised through the 50K coverage about 50K ago. I was up for a timing belt and my third set of tire.
The main issue for me was:
Coolant leak, not coming from the reservoir or the bleeder tube so that was going to be $$ to fix
Miss firing... I had the car back to two Audi dealers 3 times for misfiring in the engine. Initial starts the engine would pulse and stutter for the first 15 minutes. Then after that you could feel it on acceleration in the 2K-3K RPM range while you were shifting it felt like the engine was out of balance.
Good luck on the MB. We went the MB route but that was in the 2000 and it was also plagued with Chryslerish issues and the style changes every 2 years that they look out of date quick...
Got my fingers crossed for the GS it has 30,000 miles on it now so I was interested in reliability based on my Audi experience. Had the Audi been reliable I would still have it. It is an excellent ride, excellent handling, and great in the Snow.