I think I liked this better than most reviewers. What I got out of it was an exploration of how human colonists would communicate and share space with a native being that was incredibly powerful in ways they knew they would not understand, and also absolutely necessary for their survival. Stevland, the sentient plant that is the character of continuity for most of the book, reflects in a very thoughtful way about how he (Stevland adopts a male persona and pronoun) relates to aliens.
I do get the criticism that the way the Pacifists talk about their community makes it sound a bit YA. I wonder how this would have gone over if she had made them be an overtly religious group, and had their convictions come from their faith? In places she seems to be quoting directly from the founding principles of the Unitarian Universalists.I would say that this is "medium-hard" SF. Little is said about how the colonists actually made it to Pax. And nothing at all is said about how a plant embodies sentience. What do they think with, if not brains? I didn't struggle to believe that an intelligent and capable plant would think in terms of the chemistry it is intentionally trying to create. Stevland (the main plant) is capable of manipulating his chemical products (as many plants are) and Burke chooses to show this by having Stevland's inner monologue be very geared toward common names for what he is producing.
There is a rape scene in an early chapter that is meant to illustrate the depths to which the original colonists are willing to go in order to control future generations. Think Clockwork Orange, but in writing so less graphic. Some reviewers pointed out that the consequences of this action were not well explored.
Overall I thought the book had a lot of nuance and explored difficult topics well, and I'm glad I read it.