I just finished reading GoN. I really enjoyed the book. The Caeliar were very interesting aliens. I am always fascinated by aliens who are truly different than humans, both in their physical appearance and their cultural values. And, it was cool that they have city-ships like Atlantis from Stargate: Atlantis. The book did a great job of telling different stories but tying them together.
I wonder if the Caeliar will solve Troi's pregnancy problem, especially since they value life so much.
I am guessing the advanced civilization sent the feedback pulse for much the same reasons why the Caeliar displace intruders. They see the Caeliar as less advanced, like the Caeliar view humans. Like the Caeliar, they do not like lesser lifeforms violating their privacy.
Also, if I understand things right, the Borg basically found a way to use the Caeliar's space tunnels used to contact other civilization, as a way to travel through space faster than transwarp. If I am right, I wonder what the Caeliar will do when they discover what the Borg are doing?