I thought it was a good film for what it was. This kind of violence isn't something I like, but the film was very creatively directed and executed and there were some very imaginative visuals. The director, I gather, was trying to make ultraviolence beautiful, and while I don't think that's entirely possible or desirable, I do respect the technical and artistic ingenuity that went into it.
I was surprised by how ethical Dredd was in his way. He killed without remorse when he believed it was necessary, but refused to kill a suspect unless he was 100 percent certain of guilt. True, the fundamental flaw in his reasoning is that you can never been 100 percent sure of guilt or innocence, and that being both arresting officer and judge and jury is a conflict of interest that makes an objective judgment impossible, so the whole system is fundamentally unjust. But while Dredd makes the mistake of trusting the system, he's nonetheless scrupulously ethical in his obedience to its rules, and even shows some moments of willingness to bend the rules ever so slightly for the greater good, like when he lets the kids go.
The ending didn't work for me at all, though.