Looks like a great grocery getter on a snow covered road - not much else. What a disappointing suspension.
Let's keep this in perspective. It's a cargo van, meant, as mentioned, to carry 3K pounds of payload. Mercedes doesn't care about the articulation an off-roader might want to have, particularly if it came (as it probably would) at the cost of some highway stability. So while it may look like "a great grocery getter on a snow covered road," it's more appropriately viewed as a "great medium commercial cargo van for a snow covered road." But unlike a Ford chassis, there's no vast aftermarket of suspension parts to toss on, so people looking for a "wheeling" rig will likely give the Sprinter a pass. The 4WD will, however, be a useful addition for overlanders traveling on roads where snow or mud would cause a problem for a 2WD version.
That said, you can indeed throw enough money at a Sprinter to make an off-roader:
or even:
.
Also consider that a lot of the "fails" in the video were down to the tires, which weren't up to the mud and (couldn't tell) may not have been aired down enough, along with the light rear end. Regardless, though, the main point is the 4WD will make life significantly easier for people looking to use their Sprinters for overlanding, with little chance that the change will give good RTIs.
And now that I've said all of that . . . The video is titled "Sprinter 4x4 311CDI Test Offroad Allrad Iglhaut Low range," and given that Iglhaut is one of the top two well-known German aftermarket converters of Sprinters for off-road use--comparable, say, to Ujoint Off Road in this country--this van's setup probably wasn't factory and the performance may or may not be any indication of how the 2015 Mercedes setup will perform.