Well, I'm not a Browns fan, but, I do have a little bit of insight and an opinion:
I really like Eric Mangini. One of my favorite NFL coaches next to Gruden and Tomlin. Players don't like him because he demands a little more than RAC did. I have often found that when a "players coach" is ousted and a "task master" is brought in, the howls of "too tough," "unfair," etc. are the loudest early in said coaches tenure. Once the team starts winning, the players stop complaining. It's really all about give-and-take. Mangini is pushing these guys because the only thing they have been successful at is underachieving.
I believe Eric was the perfect guy for the job in Cleveland. I believe they will start winning...and when they do, the players will stop complaining and start respecting and understanding why he does what he does. The guy is a clone of Belichick. He shoots straight and he is abrasive at times. His intention isn't to be a dick...it just comes out that way. Belichick can get away with it due to his success. Once Mangini starts winning in Cleveland, and he will, the whining will stop. I wouldn't expect the Browns to do much this year other than improve their overall play. Next year should be when they start making noise.