My commute is 60 miles of highway against the traffic flow and I fill this CDI up once every two weeks. My 2001 E320 required refill once per week. Composed and comfortable, the integrated iPod system is a delight. Seat comfort is much improved over older models. No clatter or smoke and plenty of low end torque when you apply the right foot. Most passengers won't know it is a diesel till you tell them.
Wood and chrome trim yield a handsome interior. Don't by a 6-disk CD; get instead the $260 iPod interface cable. Cabin lighting at night is a special touch. A much bigger trunk than earlier E Class models and better heated seats.
The wheel style and size should match the E350. The trunk release in the driver's door is difficult to reach. No "rest" feature in HVAC means returning to a cold cabin in the winter.