The replay rule makes sense and is designed to streamline the review process. It also gives the referee more another resource (the NFL Officiating Dept.) to resort to while reviewing a play.
The clipping rule was altered to include the side of the leg, as well as the back. A player safety issue that probably should have been changed a few years ago.
The goalpost dunk is being outlawed because it is a celebration that uses a prop, which is illegal.