A few things were different. Stone gets killed (off-camera! but we experience the severing of his mental link) and Kallista goes nuts in a way that, frankly, annoyed the crap out of me. She annoyed me a lot in this book, and though it was intentional (it turns out a demon is affecting her, but you don't find out until the end), it didn't help. I get twitchy when one person has too much power over others and it's seen as a good thing. And surely we could have had more of Fox's reaction than Kallista's, as he and Stone were as good as brothers.
The formerly demon-possessed Godmarked also dies, also off-camera. Her son, who happens to be Stone's child as well, is the McGuffin for the rest of the plot, which involves much negotiating and fighting, but still no male/male sex [sigh].
Almost all of the story takes place in a country to the south of their home. I found this country annoying, as it was too much like the oppressive cultures of too many other Southern (read: dark-skinned, vaguely Middle Eastern) empires in fantasy, both romanticized and patronized. I didn't like the way the protagonists interacted there; they had apparently done no research before haring off on their diplomatic mission. It's all very well to infodump by having issues come up, but when the supposed ruler of a neighboring country doesn't know basic facts, it makes me like her a lot less.
Also? Obed is apparently still jealous of Torchay and vice versa, six years down the road, and it takes being drugged for them to get over it. And then they still don't have sex with each other! Clearly, this is not the book I wanted to read.
A new dude is Godmarked and integrated into the group towards the end. It's clear who he is, from shortly after we meet him. I guess the story would feel empty without another new ilias.
My opinions are more based on what I wanted to read than anything else. There are plenty of group marriage models in real human culture that are solely heterosexual. I just find that boring in a fantasy novel.