I had my E300 for 4 years now and all I can say, it is an amazing car. I don't think it gets any better than driving this car on highway. I've been driving for many year, all kind of cars and makes but this is my first Mercedes and I am impressed.
I am thinking to sell it just to buy an newer E350.
On the other hand, it's a perfect car ... why change it ?
Hard to decide :)