dobie0791, I think that the "free" maintenance is included for you too. Check my facts by searching an MB board like forums.mbworld.org I am sure this topic has been discussed.
The "free" maintenance was discontinued for model year 2005. It basically is 3 oil changes, a brake fluid change, and one inspection of the car and brakes. It does not include wear items (brakes, wipers, tires, belts).
If you do your own oil changes, the free maintenance doesn't add up to that much. If you have the car serviced at the dealer, a simple oil change will cost you about $250 there, so it does have value for those owners.
I agree with G-Man II (you will do as well or better with 6 month 5k mile OCI with any conventional oil in the US); I just prefer a longer OCI where possible. I suspect that the ACEA A3 requirements are for driving conditions that are not replicated in the US unless you are racing the car on a track.
The truth about MB, in my opinion, is that the reputation of old is no longer true. The old mechanical injection diesel cars, that with proper maintenance, would last for nearly forever is long gone.
I am not worried about engine longevity. The rest of the car will fall apart before the engine and will be cost prohibitive to repair. Electronics, transmission, air suspension, air conditioning, etc.
In fact, my car comes equipped with what they call SBC brakes. Instead of a master cylinder, the brake pedal is a switch connected to a computer controlled high pressure electric brake fluid pump and reservoir. There have been a very few case where the system fails, and the backup braking system has no servo boost and only works on the front brakes leading to extremely long braking distances. I have seen rumored online that MB is going to discontinue SBC (is it cost cutting? is it liability concerns?). The S430 you bought does not have the SBC braking system, but it probably does have the air suspension called Airmatic.
My point is that the cars electrical failures will doom the car long before the engine dies.
I think that the currently produced longest lasting car that can be easily repaired for the long haul is a Toyota Corolla!