Only the good cops who believe they have nothing to hide are happy with the cameras. And it is true, they deal with a lot of shtupid people doing shtupid shit. That you really need video footage to believe, it is that shtupid.
But, how many times has footage mysteriously disappeared. Or the footage wasn't allowed into court. Or the police officers wouldn't comply with the subpoena for the footage. Again it is everything... will be used against you. (and nothing will be used for you)
So, in the end. The good guys will do good, and the bad guys will do bad. With or without a camera. So, in some instances, it is just the same as it was before.