I've got a 300D w123 and really like it. Then I got the 300SDL w126 and now my wife drives the 300D... she doesnt like the size of the SDL and that is fine with me, because the SDL is really a great car. So far parts and such have been pretty cheap and easy, just shop around. My indy mechanic lets me bring parts in if I am out of my league on a repair, so that helps keep costs down too.
Now, I might be complaining next week after I work on the a/c on the SDL...
