For racking up the miles it is hard to beat a good, properly maintained 98/99 E300. That is what the wife daily drives and she averages around 3k/month. I do like the W211 cars a lot and am in the market for either an 05/06 CDI or 05-09 E class with the bluetec. With the exception of the high priced motor oil and the occasional seal replacement there is nothing wrong with the bluetec engines in my opinion. It is just a little more cumbersome to deal with under the hood but a big positive is not having the SBC.
I had a customer bring a 99 E300 (~250k miles) to the shop the other night that he was considering purchasing. It was a little low on power but the asking price was only $2000. Found the boost signal tube from the intake to the solenoid off, replaced the rubber hose with a new piece, hooked it back up and poof, he had power like it should have. He ended up purchasing it for $1800 and the a/c worked great in the car too
. It was a steal if you ask me.