We have a 2006 Winnebago View with the Mercedes 5cyl. We have put 45k miles on it in the last year and a half with no issues. We get 18mpg and the engine runs smooth. I'm a closet gear head and would not have purchased a RV without the diesel and seeing that the Sprinter Chassis is used on FedEx delivery trucks, I was sold. I do all my own service work - which Mercedes makes easy (at least oil changes, which are much easier with the filter removed from the top).
I plan on driving this diesel Sprinter for many years to come.
Good luck.