Since I do a lot of highway driving, at times in bad weather conditions, I feel I need a SUV. This MB beat my previous luxury Japanese SUV hands down, in terms of ride, braking, offroad (something the previous SUV just couldn't handle)and mileage. It sure cost more but the extra cost is worth it. Mileage is very good and one can't tell that it's a diesel engine. Using the cruise control significantly enhances mileage on highways. The transmission and engine deliver power smoothly. Diesel engines beat out hybrids when hauling heavy stuff and the ML320 has class-leading towing capacity. So far, no problems with reliability. Looks like MB has fixed the problems of the previous generation.
Mileage, spacious interior, robustness, durability, braking, towing capacity, cleanliness of the Bluetec diesel (reduces my guilt), safety ratings.
The "famous" placement of the cruise control stalk. Could get pricey quickly when loaded up with options.