I just removed a set of Marathon Plus from my commuter and couldn't be happier that they are gone. They were the absolute heaviest and most unpleasant tires that I have encountered. They are not worn out but I just couldn't stand them, every pedal stroke felt like I was riding in sand and the ride was terrible. I replaced them with Michelin Stargrip winter tires and even spongy, semi-knobby winter tires roll better.
For some people, I guess the flat protection is worth it but for me it is just overkill.