Well, as of today, I am a big fan of registration.
Situation: Haven't been to the field in a while due to work etc. (it takes me 1 hr to get there) so I decided to keep my thumbs up to date by taking my 64MM F-18 to the local park. It being a weekday and 2pm, no one was there, which is my personal rule for flying anything in parks. If there are kids and/or people around, I don't fly. Anyway, after the second flight, I hear "sir, sir" behind me and turn around to see a cop coming my way. I had just landed and was retrieving the plane, so I walked up to her, plane in hand. I don't like cops, but I made and effort not to start off with "what's the problem".
She tells me the PD was called by an individual complaining about my flying - saying I was too close to the airport. She asked me if I had ID, and I handed her my DL and the FAA registration. She looks at the FAA card and says: "so, we've been wondering how this works". I then explained about the requirements, how everyone has to be registered as of this month, the safety guidance, the fact that FAA controls the airspace and has jurisdiction over local use, etc etc. By this time, her supervisor, a captain has walked over. She explains it all to him. Also by this time, dispatch radios in to say the local airport has no complaints. Then I explain about the AMA, modelers vs drones, that we too are upset by poor judgment of the drone guys and understand the concerns etc. I indicated to them that everything, including an LEO "kit" is available on FAA.gov. By this time, the captain had brought up the website on his ipad, and stated to her "there is no issue here - we will educate our guys on procedures here".
And that was that. That FAA card saved me a lot of trouble.