I can't imagine buying from an unproven truck manufacturer. Stick with what works, and cheaper. Looks pretty though.
Mercedes has a huge amount of experience with trucks. The Unimog was already mentioned, but they also built the G-class as a military utility vehicle. They have a thriving heavy equipment and truck division that builds a lot of the heavy commercial trucks from Europe to Australia and Asia.
The things that makes me balk at a Mercedes Benz pickup are the electrics and the lack of dealers outside major urban centers. Most backwater mechanics can work on a Nissan or Toyota because they are pretty common, that same mechanic probably has a stash of GM, Dodge, or Ford parts in the back because that's what all the farmers and rancher own. If you roll in with an ailing Mercedes, you are probably looking a several hundred miles out of your way to a certified dealer. Mercedes and the Volkswagen Auto Group both have had problems with their over-complicated electrical systems. They put so many farkles on their vehicles that there is much more to fail. Even the old W123, which is hailed as a million-mile tank and the 190 which is lauded as an unkillable cockroach have a slew of problems. None of them keep the cars from running, but even back in the 80s and 90s Mercedes was over-complicating things. Go find a W123 or 190 that has everything working properly.
A friend of mine was an auto journalist and even the press cars were plagued with problems. On one he logged on average one electrical fault per hour for the first 8 hours of a cross country road trip. He had to pull over repeatedly to "reboot" the car only to have another system crap out.
For the price of a Mercedes-Benz, I would much rather buy an FJ80 and pay an expert to go over it inside and out or a low-miles FJ100.
EDIT: Seriously, Mercedes?
No dropgate?
1970s brown velour?
I think I just threw up in my mouth a little.
This one isn't much better, it looks like a doodle in a middle schooler's notebook
Speaking of "fail"gates:
That might help keep stuff in, but it will have a terrible effect on fuel economy. The tailgate actually creates a vortex in the bed that helps the truck slip through the air more efficiently. Water spray and dust will be sucked into the bed, covering your gear with grime; plus, you can't put a topper on this to secure your gear.
I know these are only concepts, but c'mon!