My 1989 Ford T-Bird Super Coupe has an Eaton supercharger which, after 150,000 miles, is still going strong. The front oil seal is leaking a little, but not nearly enough to take it apart and repair it. The rebuilt front "nose" unit is available from Eaton for about $ 450 exchange. Can't speak for the M-B units.
1986 560SEC: 150,000 miles, runs great, but I've got to sell it (too many cars for one man)
1987 560SL: 122,000 miles, used to run poorly, now (thanks to forum), runs great!
1997 GMC Jimmy: Turned out to be a turkey.
1989 T-Bird Super Coupe: 150,000 miles, still runs great. Ford got it right.