well, without getting really involved, all i can say is that i have worked on them every day for the past 6 years (came over in '02) and i will say that the older ones (02-06) arent terrible but arent great, the parts $$$ will kill you. the electronics on them are extremely finicky, and VERY expensive. after large electric storms i get a rash of control modules that have given up the ghost. the brakes are smaller than those found on a ford taurus. the transmissions fry like bacon if not serviced every 50k, and costs more than your e40d.
the new ones (07+) are JUNK!!! you are right, we cant keep them on our lot (we are the #1 sprinter dealer on the east coast last i heard) but we also cant keep them from being towed back into the service lot!!! junk, junkity, junk junk junk!!! i have dropped several cradles to replace parts that the robots forgot to weld, stainless steel exhaust bellows that crack and cant be accessed without dropping the cradle, 32 electrical modules that lie to each other causing all sorts of stupid problems. software revisions that change every 5 minutes, each one fixes one light, and causes another. engine wiring harnesses that are routed so poorly, and so tightly, that they are chaffing through at 5000 miles, and they pay around 20 hours to change them. if someone chages their oil, and overfills it by a teaspoon....it will cause excessive soot to build up in the egr cooler and clog it, the fault throw derates the engine so you can tow it or drive it in at 20mph, and then close to about $2000 worth of parts needs to be chaged. these vans are a nightmare.
the ups rep has told me that they wont be buying any more sprinters, their shops hate them, and the price for maint./tow bills is astronomical, and counteracts the fuel savings.
also...the mpg ratings are an empty rating, that drops off quickly if you load it.