I actually test-drove a V12 before I started buying 6.9s. They're beautiful on the inside and have everything you could want, including a lovely sound system. They go like the clappers, but the traction control always spoils the fun. Unfortunately I found the experience rather insulated and detached. So very quiet, with no V8 throb, or even the mechanical noise of a V12. They're huge to park and it's very difficult to have an idea where it starts n ends. I wasn't particularly fond of the exterior style (too square and bulky), but the fact that they were listed as a high powered vehicle (prohibited for probationary drivers) had me intrigued.
The example I drove was cheap back then and a lot of car for the money. But it wasn't the best example and various things had me concerned. For starters there's a high percentage of plastic. Over time these things break and cannot be repaired successfully. Critical parts will fail and these include wiring sockets & plugs (of which there are plenty). MB decided to use lots of plastic in the engine bay and with all that heat many parts don't last (one example was the dipstick handle).
This was the era when MB also decided to use diagnostic equipment that patched into the computer systems on their cars. Being so complex, with so many ECUs they probably didn't have a choice... Without access to diagnostic devices it'd be a real challenge to find faults.
Almost everything was motorized and it's only a matter of time before things require attention. Again many parts contain plastic components that were never designed to be taken apart. Even if it was possible to disassemble parts, they're that complex it'd take hours to determine the problem and then go about fixing it. For some reason I have flashbacks of my brother's VW Passat!!
The computers aren't fixable and if you are lucky enough to be 100% positive an ECU IS faulty, they're huge dollars to replace.
MB also introduced hot wire air flow sensors and fly-by-wire which I never liked.
Many special tools are required and I think the mid nineties was when MB started using Torx bolts. They also lost the plot with model designation, as a 600SEL suddenly became a S600L. I could live with that, but it was all down hill from there.
They weren't that popular with the public and as a result they're fairly rare. Rare means $$$$$. Even the MB enthusiast that I just met (who had a partitially dismantled W140, along with many other earlier MBs) said they're a nightmare and one should stay away!
I really hope that all these issues aren't present in all post-W140 MBs. I can say plastic does feature quite heavily. The trend is towards throw-away now and that philosophy probably applies to all marques....
Bear in mind that I've never owned a W140 and that's probably because (for once), I actually listened to my gut instincts! I'm sure my hip pocket and bank manager will one day thank me!!
This also highlights why I chose the W116; a contemporary car actually designed for the M100, with chrome (not plastic) and parts that can be disassembled and repaired. An only one damn computer!