I was recently gifted a free pass to MNC by a friend on Steam. This friend, like myself, was religiously opposed to MNC under the premise that it was simply a TF2 copy. I played it, and it does have things that seperate it from other games and make it interesting, but ultimately it felt too simple and derivative.
During one of my trips to Valve I had the opportunity to interview Robin Walker about a number of things, and one of them was how Valve felt about games that seem to blatantly steal from them. I should note the difference between "theft" and "inspiration" here. There are plenty of games derived from other games, for example, Minecraft is aesthetically very similar to Infiniminer, and Infiniminer's ideas had been inspired by games that came before it. Robin modestly said that the majority of TF2 "imitations" can be attributed to reaching "logical gameplay conclusions", that many developers will "copy" each other without even knowing it. He brought up the fact that many players said TF2's art style looked like the Pixar-style used in "The Incredibles", but TF2 had looked the way it did long before anyone knew Pixar was working on the movie.
Despite the fact that MNC differentiates itself with a few interesting ideas, I can't shake the feeling that it has no soul. The character's voices are annoying, and each class seems to simply be a pallet-swap of something from TF2. (Both Snipers make fun of gamer culture and have identical loadouts, both heavies are big guys with chainguns and "weird nationalities", etc)
Overall MNC just left me feeling indifferent and totally unmotivated to start it up more than once.