I am going to give one last shot at this. Out of the other thoughts and opinions others have provided which I thought were quite good IMHO.
The site in particular "The Paracast Community", I understand you had your moderators take a test ride. Did you happen to have your members take a test ride as well? Setting up an imported test site so their accounts were still active and have them give it a go before making the switch?
I understand you may have had good feeback from your other two sites, but they are small and barely any activity(not trying to be rude with that comment) so the opinions are from a smaller consensus. With your larger site you have more people to please and if they are active, they also want to be active in decisions made for the community, not just something that is thrown on their lap.
The opinions and criticism that were given by other people in this thread which again I thought was great IMHO were about how to go about dealing and making things better. Ways to word comments and make them feel that their feedback is appreciated.
Like I said earlier and I should have stopped then.... good luck with your community.