Mitaka

I am back on the market for a new family car. I miss my A8 big time. I just could not deal with the repairs anymore. So I figured I'll get a Q7 (is it improved in terms of reliability) or Mercedes R Class (CDI) seems very attractive. Since I value the opinion of this forum so much I wanted to place the thread here and see your opinion. Those of you who have had a Mercedes could you please advise me on a good discussion forum??