Corrosion is a big problem in my case. There was a recall last year and had something to do with the front suspension. Apparently when they fixed the recall, they found out that corrosion had started in the area. MB painted it under warranty but still, left a bad taste in my mouth. Just after the warranty expired, corrosion started in my trunk but they wouldn't fix it.
The E420 does not drive like a Mercedes. It doesn't give me the same feel as the W124 gave me. It just feels like driving a Camry or Honda. The interior looks too plastic IMHO. I wish I didn't sell my W124.
Hope it helps.