Yes, my wife and I (Carnival Diamond) also applaud this decision. We have been on many cruises with no issues, and no conflicts. We have also cruised with our children when they were teens. I would easily say the majority of cruisers are respectful, and many parents are mindful of their children. However, it does not take many to really create some havoc. Like others have said, we have been disturbed by the running and screaming. We have seen much reckless behavior. In April of this year (Vista), we had to call security due to the 4 children in the cabin next to us. They were running up and down the hall, screaming and slamming the cabin door. In the cabin the were fighting and throwing things at each other. I stuck my head out of the cabin when they came out once and asked them (politely) to keep it down. A boy of about 15 cursed me out. Then we called security. Security came to the cabin and stopped the commotion and stayed until the parents were located on the ship. In May, also on the Vista, we had all of our cabin decorations stolen (some rather precious to us) or destroyed.
Tony, on his "La Vida Loca" YouTube CruiseOn report today supported the curfew. He said there was some backlash from people calling this "parent shaming." Really? Some also quoted the old line, "It takes a village to raise a child." Well folks, a cruise ship is not your child rearing village. While a few parents feel they paid big bucks for a vacation and don't want to spend it minding the kids, a few thousand other passengers paid big bucks as well. And they don't deserve to be hassled by YOUR unsupervised children.
So, yes, we do think it was time for this. We also agree with other commenters that it should be earlier; midnight or 11pm.