The issue is that it needs to be used consistently, at the minute some things get reviewed and others don't unless one of the officials raises a concern.
If it is to be successful I think it should be like cricket or tennis where the number of reviews are limited if you keep reviewing rubbish, football is not like rugby where they play advantage and have clear breaks in the game where they can check something, with the refs miked up it tends to work quite smoothly. Too many whining asses in football that will claim for everything and have no respect for the officials.