This car is what it is, it's no sports car but it's not designed to be. However it fulfill its design purpose perfectly.
It is amazingly roomy in LWB form, and actually it's very nice to drive. The steering is pretty vague and a bit heavy, but it's no trouble at all to use. The autobox is smooth as silk, it's a 5spd with tiptronic, but I used it once and then just left it in D!
It gets through brakes and tires quite quickly, but parts aren't expensive really.
I get the car serviced and MOTd annually at a german car specialist, and it's been perfect, however between MOTs 2008-2009 it only did 1500 miles so I would expect nothing less.
The ride of the LWB model is far superior to the standard length car, and when fitted with original spec Goodyear GT2 tires, it cushions very well, better than rubbish ECO tires we tried on the front for a while.
The Avantgarde is a good spec level and looks smart, being sportier than a Classic or Elegance. Spec includes half leather, A/C, 4x electric windows, cruise control etc etc very well appointed.
It cruises very well, and 5th gear is very tall, so economy on a run is excellent, at least 40mpg.
It overtakes very well and stops quickly and smoothly.
Don't go to Mercedes dealers for service though, the service is poor and the prices immense.
Nothing has gone wrong ever, and it will last many many years at this rate.