I have a 98 E300TD with 44k miles, and the only thing I have had problems with are with lights -- brake, tail, rear, license plate, etc. It seems a light goes out about every 6k miles. Sometimes, though, it turns out to be the (mechanical) socket connection not the actual bulb. If the socket rusts or degrades, eventually the continuity will be affected and the MB dash will show a light out.

But even if I knew this, it would not have changed my buying decision. It's a great car.