New diesel owner here...
After finally deciding to go with a GLK250 BlueTec, I can't figure out why I never got a diesel before. Sure it's a tad sluggish on the highway, but it has 370 ft lbs of torque and gets 34 MPG. Makes as much noise as my 328i and no smell/smoke/etc. Gotta say that I'll always have one after this guy.
Also, my wife's a pretty big fan of the "D".

(professional driver on a closed course...

)