If you're looking for a luxurious way to get around with family and friends, the Mercedes-Benz R500 is a great solution. I've really enjoyed the quality feel and luxury appointments. I also own an S500 and much to my own surprise, I've come to prefer driving the R500. We have lots of guests and family so the R500 is great for us. The car drives very well and gives you the feeling of a powerful SUV. The luxurious interior gives you the feeling of the S500. This car is the best of all worlds.
The Keyless Go is one of the best features and makes fumbling with keys a thing of the past. The Comand system and navigation are wonderful. The mid and rear seats have far more space than I had expected, and more than I've seen even in mini-vans.
The only improvements I can think of would be the back doors, which seem too big. They also make the mid section look minivan-like. The trunk is really small since most of the interior space is used for passenger comfort.