Well we have a 2001 CLK cabrio 320... and have not had one thing done to it, besides an A service. The car now has 12k miles on it, and hasn't been back to the dealership!!
The ONLY complaint is the way the windows meet the top (with top up). You can't EXPRESS them up because the window doesn't fit in the rubber lining properly, thus partially opening back up, they must be in the -before resistance point- UP position.
As for the S-class, we had a W140, 1999 (don't know if this counts) and the only warranty work we had done was a failed vacuum pump (for pneumatic doors and trunk) and a loosened center rear-view mirror, both fixed under warranty, with no hassles.

Things I do notice about newer MB decreasing quality:

1. Not a matching spare anymore! (still full-size though..)
2. MUCH less leather on door paneling (IE: 94-97 C-class had full leather doors; 98-00 C-class had very little leather on the doors, and some flat ugly paneling instead!)


And BTW, I have never relied on CONSUMER REPORTS or JD Power Associates. My personal experiences have proved them SO wrong it's sickening... I wouldn't trust that BS with a Ford!

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)