I know its not as poweful as the M119, but the old 24-valve straight six delivers such a wonderful chorus when getting up to its 6400 rpm redline it brings tears to my eyes. That wonderful German gutteral six sound echoing back into the cabin off of buildings you pass by. Like my old '85 280SEL(I NEVER should have sold that car. I loved it to death, but so did winter salt).
Also, I believe that wonderful sound is what the new V6 lacks. It doesn't seem to have the same character as the I6. Of course that's just my opinion.
My W210 already has the 2.82 differential with overdrive.
As far as fuel economy, with the overdrive I have gotten as high as 27.5 mpg. Usually average around 22 - 24 mpg 'round town.