My personal experience is that they were good and reliable until 1990.

I have been driving a 1995 S500, ( Bought it used, STARMARK at 22K miles and bought 2 extra years of MB Warranty )
at present I have 55K miles.

Its troublesome for two reasons:

1. I think the quality has gone down.
Second, Is the problem with MB Authorised dealer.

In my first year of Starmark warranty, dealer was very cooperative. However in the second and third year of STARMARK warranty, dealer had no interest in fixing warranty jobs. My car had to be sent back second and third time to fix the SAME warranty job correctly. So the quality of service has also become POOR.

Car was never returned on the same day as promised, but usually after 2/3 days.

Dealer's service department NEVER returned your phone call when the car is in the shop. Heard his complaint from other users also.
While waiting at the dealer to pick up my car, which was never ready at promised time, I had the pleasure to watch other customers express their frustration and anger for the quality of service and repair jobs.

I hope MBUSA are reading this post. They have to fix the problem of Quality of the car and quality level of their dealers.

I am hearing great reviews about quality and SERVICE from my friends who drive LEXUS.