I have a '98 E320 and 2001 SLK320. Both have been very good cars with few problems. The SLK's has never had a problem, although it has less than 7K miles.
However, I would not buy another Mercedes given the decreasing quality of these cars. When I look at the '03 E320, I see little styling distinction from other new MB models as well as other manufacturers. The interior looks and feels cheap. MBs are no longer are a good value. I would be upset if I were a new S class owner and people would mistake my car for an E Class. And the same for E Class owners vs. C Class owners. Again, little styling distinction. BMW may be way out there in styling lately, but at least their models have a distict personality.
However, a friend of mine is taking delivery of his '03 E320 this week. This is his second E320. He knows that quality has been going downhill, but doesn't care. He still wants the prestigous name, and if there are problems, the dealer will fix it under warranty. He replaces his cars every 3-4 years.
I can only keep my fingers crossed that my MBs continue to offer good service to me.
2000 Lexus RX300