Today I drove a 1996 S600 with 40K miles and a 1996 SL500 with 60K miles.
All I have to say about the S600 is "WOW".
The amazing power, ride, handling and the extremely tank-like feel of the W140 chassis make me absolutely love this car.
I couldn't manage the brake the tires looks from a stand-still (ESP I assume) but did manage to get the drivers side wheel to leave a nice strip around an aggressive corner, thanks to the "posi" rear end.
The power of this car is something to behold. I put my foot to the floor on a road, about a 1/8 of a mile from a stop sign, I ran out of road at 5,000RPM just when the engine was coming to life, and I was at like 60mph already. Just WOW.
I wish I had the chance to take it on the highway, but didn't. If I did, I might not have a license right now

Simply amazing.
The SL500 was a toy in comparison, not impressed at all after driving the V12 beast.
Pix of both can be seen here:
http://www.unusual-imports.com/002-002
http://www.unusual-imports.com/002-003
Then I had to drive home in my old diesel, which really sucked after driving a car that was $140,000 new.