I'd recommend hitting www.sprinter-source.com and getting the info from people who use the vehicles on a daily basis.
The good:
MPG
Decent reliability.
Great cargo/towing capacity.
The bad:
Not many Mercedes or Freightliner service depots for them.
You will pay Mercedes prices for parts and Mercedes prices for labor. A clogged DPF will run you north of $3200 (which is why you don't want to idle the engine constantly.)
The OP apparently wants a class "B". For a van (as opposed to a class C chassis), a Sprinter van is light-years more comfortable inside than the Chevy vans.
However, if the OP can wait until next year, the "B" market is going through its biggest upheaval in over a decade: Dodge has their RAM ProMaster already out and upfitters are working on that, and come summer of next year, Ford is coming out with the Econoline replacement, the Transit. Both offer 90% of what a Sprinter does (including good MPG numbers) for a smaller price tag, and one can get a gasser model.
The Winnebago Travato is the first opening salvo for the new ProMaster "B" vans. Sportsmobile is in the process of upfitting a ProMaster, and there are other companies which are working on models.
If you can find an older T1N Sprinter "B", that might just be the ticket. Make sure to replace the turbo resonator with the aluminum aftermarket, and those 5-bangers are very reliable. However, the T1Ns do hold their price.
If I had unlimited time/money, I would order a 2015 all wheel drive Sprinter next year (I'm guessing Mercedes takes orders in May for a September delivery like they did with the 2014s), have it upfitted by Sportsmobile as an all-diesel rig, where the stove, generator, water heater, furnace, and refrigerator would be all running from the diesel tank. It is expensive, but it would definitely be useful for boondocking, just due to only worrying about one fuel.