To answer the question: "'I've always wondered what the secrets to a great ragchew net are?",
For me, I have participated or listen to many nets (mostly VHF / UHF) in States or Territories I have visited or lived in. My experience has been, location, education of and experience of the individuals, who is the group, what is the group about (ARES / RACES / Skywarn /Social), and what topics are being brought forth. As for the Emergency Nets, I beleive we all know these are not rag chew and they are to the point, BUT! discussing how to improve them? how to train others? I think would be a great net.
One example was a daily net in the Greater Dayton , OH area. They met everyday and discussed the Jerry Springer TV show. Good number of participants, but, not everyone's cup of Tea. Another net that was fun was in a Metro Town that had more than 4 repeaters tied into the network. Here topics based on Amateur Radio where asked. One night they brought up Antennas, and it's fixtures (as in towers), and what Federal, State, County and Association R&R and laws were in place, and how everyone had dealt with them.
Talking to YL's at the Orlando Hamcation this year, they mentioned that simple Q&A of Food, Restaurants, Hobby Stores and other simple none technical was their favorite nets.
Now, since I made a left hand turn and not answered the Question directly, I have to say that a good net requires dedicated, enthusiastic, disciplined NC Op's with great tact and feal for who is participating, their years of experience and knowledge.