I havent towed with it personally, but the mother in law has a E240 petrol. In her words, she would rather tow the horsebox with that as opposed to the L200, the L200 is used basically due to the 4x4 and additional weight, obviously wanting the tug to be heavier than the trailer. I have driven it, and I must say, for a 140,000 mile car that is 13 years old, its a fabulous drive and is still well put together without age related rattles. I dont think it has been hideously expensive to maintain either - I seem to recall a set of front brake pads being cheaper than my Ford Escort at the time! Depending on age, only thing I think is a point to note is that the W210 range has had problems with corrosion.
Cheers
Rob