Nothing till now, but it is very advisable to do regular maintainances.
The car is very good at all, It is fast, silent, and of good Mercedes quality, as previous models like the W123. My car has the sportline feature pack, which makes it a little uncomfortable compared to standard, but is is more fun to drive.
My 1994 Mercedes E420 is an over all a wonderful car. As a previous BMW owner, it was truly a different experience. What is most attractive about it is the simplicity of interior, with little, or not extra-complicated gadgets. The interior noise level is wonderful, and very little engine noise at any engine speed, especially in idle mode. What is lest favorable about it is the way the transition reacts. Though it's smooth, but very unresponsive.
I have owned my 1994 E420 since September of 2001. I have driven it across country 3 times and have never driven a nicer car. I used to rent many cars for work when I traveled and I have probably driven over 20 models extensively. The E420 is the best car I have ever driven or owned. I have cruised across Montana at 95 MPH and the car has begged to go faster. My car has almost 200,000 miles on it and has required many repairs, but I would not part with it for anything. It is quiet, smooth, comfortable, and everything I would want in a fine automobile. My plan is to keep my E420 and restore it to better than new condition when I am able with after market ignition and exhaust system and improved suspension. This car is a keeper. I love this car. I see newer Mercedes that look nice but have no intention of trading for a newer model. This is the last car I will ever need, as far as I'm concerned.