I'm nearing 100K on my 2007 Sprinter and only problem was a injector went out covered under warranty. Changed out the shocks and the ride is better than most cars. So once to the dealer in 8 years 100K miles - I can live with that.
Some guys on the Sprinter site are getting upwards of 800K miles on their Sprinters.
I agree service can be scarce in some out of the way places. In every small town you have a Ford/Chevy dealer, but not Mercedes.
I will say this it's been to the dealer less than the Fords and GMC's I've owned.