I think I would look at using it after games for diving to start with. My fear would be that refs play it safe knowing that there could always be a review. I think they could develop the habit of not making calls, and letting the camera do the hard work for them, but if there is only one challenge then that sort of habit would result in a worsening situation.
Missed calls are going to happen regardless. I think if they needed to worry less about making calls when a guy is rolling around on the ground, and could be freed up to make the call only when they have clearly seen an infraction, with the camera there to red card either a diver or an actual guilty party in any case, then the refs could be able to focus on some of those other bigger calls.