reliability...E420 1997.
Ok,
I've had my 1997 E420 since August 2005. I've put 32,000 miles over 21 months of primarily stop and go traffic commuting.
Only one issue, the transmission control module failure, forced me to drive the car in for immediate service. Put another way, I haven't had to call a tow truck yet, unlike my old Jag, which has been on a Flatbed truck 5 times in 3 years.
Check out my car's photo's:
Mercedes-Benz E 420 page
Here's a breakdown of what I've had to do outside of regular maintenance, oil, filters, brakes, etc:
-72,000 Miles- new Bilstein HD shocks (<$160 dollars- self install), a must have replacement, extreme ride improvement.
-80.000 Miles- New headlight lenses (<$180 dollars- self install), another must have, as the old ones were quite faded.
-92,000 catalytic converter failure ($800 for cheap replacements- Midas)
-92,000 Miles- New spark plugs, ($10 dollars- self install) no difference in performance, although the old ones looked quite worn.
-100,00 Miles- ($900 dollars- AAMCO Inc.) Transmission control module, speed control module.
The other item that can go out on these is the oil tubes (I believe), but these can be fixed quite easily if you do it yourself. From what I've read there isn't much that should go wrong in terms of major items in the engine and transmission. I've heard that window regulators and sunroom motors sometimes give out after 100,00 miles, but I am planning to put another 100,000 miles before this car retires...