The 500E is a special car. Built in collaboration with Porsche, it offers a powerful DOHC alloy V8, widened fenders, and sport tuned suspension. It was built at a time when cost didn't seem to be an issue. At first glance most people think it's just another E-class sedan so it's quite stealthy.
In my opinion, there's only two things wrong with it. It's heavy and it doesn't come with a manual transmission. At 3855 lbs. you feel its mass when cornering and/or braking hard. Not that it doesn't do either well, it comes with great brakes and the suspension does a great job of hiding all the weight. But you can definitely feel it. The 4-speed auto works ok, but a manual transmission would really make the car shine, imho.
If 0 to 60 and 1/4 mile times are your first priority, the current crop of AMG models are far superior. If, however, you want a small piece of Mercedes Benz/Porsche history and like conservative yet aggressive styling the 500E is hard to beat.