All the blather, opinions, and purely anecdotal "evidence" is fine, but let's see what the very company which designed and built the vehicles has to say.

"The vast majority of all Mercedes-Benz cars and all Maybach, AMG, and smart vehicles with gasoline engines can be run on E10 fuel.

"Exceptions include: the first generation of four-cylinder direct injection engines [Europe-only]; as well as vehicles in which a 3-way catalytic converter is not installed; or, vehicles with carburetors."

Above is my own translation from German. An English-language version specifically for the U.K. is here:
http://www.daimler.com/Projects/c2c/channel/documents/1991242_Daimler_Bioethanol_fuel_E10_unsuitable_vehicles_en.pdf

I temporarily cannot access MBUSA.com, but they also have posted a notice to customers stating essentially the same thing. Note that 10% is the maximum ethanol percentage of any non-E85 consumer fuel sold in the U.S. currently - one erroneous post to the contrary notwithstanding.