Hi - I too am looking at the same vehicle '03 4matic with about 40K miles. Has good carfax although I have not seen specific books and records. The posts make it seem like '03+ were the ones to get for this generation. How has it been so far? I recently sold my '95 W140 S500 which was fantastic! I hesitate when I see so much plastic in the new ones. Thoughts ? I also have found a 560SEL and a 450SEL both of which look in really good shape.
Mr. Mazza, you ask excellent questions, and the answers are matters of taste and mission statement.
First, on the mission statement, if you're in a climate where the car will see ice and snow, or even lots of heavy rain, 4Matic is a tremendous plus. That rules out the earlier cars.
Second, as to taste, I also enjoy the immense solidity of the '90s S-Class (W140) cars, but not their relatively lumpy handling; they're not anywhere near as much fun to drive as the 2000+ S-Class (W220) cars.
The first few years of W220 had too much plastic and too little build quality, but by 2003 that was well sorted out. My car has just as solid a feeling as the late-90s S500s and S600s I've driven, and is just as quiet and comfortable, but is an absolute blast to drive on twisty roads.
The computers controlling throttle and transmission really do adapt to your driving style, and my car now knows very well how to scoot, and to hold each gear to redline when I floor it. It's LOTS of fun when that makes sense (particularly with the AMG staggered wheels and the right non-winter tires), then I set the air suspension to full soft and it's a peaceful long-haul cruiser for four adults of any size.
Everything always works, and my dealer is amazingly good at supporting the car.
There is one weakness I know of in the '03-ish cars compared to those from a few years later, which is the seals at the tops of the front suspension struts. The older design can leak air over time. The new replacement parts do not leak. If your car is still under warranty, these seals can be replaced with that coverage.
One minor nuisance with the '03 compared to the '04 and later is that the nav system uses a deck of CDs rather than a single DVD to cover the US and Canada. On long trips, I need now and then to change discs. This has not turned out to be a major nuisance. MBUSA continues to make updated CDs available for this generation of nav systems.
The phone system adapts cleanly to modern Bluetooth phones by replacing the Moto V60 phone that came with the cars with a "puck" sold by M-B and third parties that speaks Bluetooth to your phone and looks like a phone to the COMAND system. Result is smooth integration of all features and high quality handsfree operation.
I could go on and on, but I think you can see that I heartily endorse the '03 S500 4Matic!