They will break if they have been driven a certain way for donkeys years then the new owner changes the way the car is driven - it puts weird stresses on old cars, especially heavy, automatics like the W124 - belt it and it will disintegrate. I think Autocar were poorly advised about buying an Estate W124 to be honest.
If the aim was to test the W124 as an everyday proposition then the Estate is maybe the wrong choice as they get hammered for obvious reasons. Pound for pound (the object of the excercise as far as I can tell) the saloon is a much better choice as they seem to be bought by people who look after their cars. I also think the pre-facelift cars are much more reliable as they tend to have far fewer electric options fitted. Subjectively they have more of the Merc 'heft' as well.
Robotboogie makes a good point about the handling - the soft suspension allows for high speeds on what now passes for roads in this country. I've got an E220 saloon at the moment, a very late 95' model. It can be fun to drive - either you cruise at Taxi speed or drive like you are on an Auotbahn - anywhere in the middle and it wallows.
Thing is, other cars do seem a bit flimsy after a W124 and nothing else is anywhere near as comfortable. I've had four of them in a row.
Bring back Steel Wheels.