I recently finished this book. I thought the cliffhanger ending was very powerful and made me eager to read the follow up. As for the rest of the book, I thought it was a bit of a mixed bag.
To be honest, I hated Rough Beasts of Empire, and in particular DRG III's take on Sisko. With Plagues I think he stuck to his guns on his take on the character while also giving readers some much needed scenes between Kasidy and Ben. With Plagues we finally get to see how Kasidy feels and what she thinks about Ben's actions. And perhaps its my imagination, but I would like to think that DRG III took some of the criticisms of his take on Sisko to heart and they were voiced by Kasidy. I'm still not a fan of Sisko's decision, but at least with Plagues we got that dialogue between the characters and something of a truce between them. Also it was good reading Sisko's scenes with Rebecca.
Regarding some of the other characters, I thought the Tenmei scenes were written with great tenderness but I felt the Elias Vaughn story is being drug out. Either kill him or restore him to full health. I don't see the need to continue the coma story when that page space could go to some other character.
Compared to Rough Beasts, I don't think Plagues was as disjointed. However I don't think the Enterprise or Spock were needed. I don't think Enterprise was needed at all and I don't think that Spock was needed outside of wrapping up his time on Romulus. I wish more time had been devoted to fleshing out the Robinson crew. I'll admit that I'm a sucker for new crews, but with Robinson, I still feel the crew is a bit bland. I wish the book had focused more on Robinson and DS9. Enterprise's inclusion felt unnecessary. And I wasn't a fan of Geordi's voluntary demotion.
DRG III is a solid writer, he pays a lot of attention to detail, and he had a pretty good grasp on intergalactic politics, but admittedly Plagues was a bit slow going. It picked up speed toward the end, but I think there were too many characters, too many storylines, and I wish the book had been leaner and meaner. Perhaps if it had just been a DS9 book instead of a Trek book, DRG II wouldn't have needed to tackle so many storylines.
Overall, an improvement over Rough Beasts, but a dry read, saved by some good character work and one of the best Trek cliffhangers ever.
So far, there hasn't been a Typhon Pact book yet that has really capitalized on the Pact's potential, IMO. I'll see if Raise the Dawn changes my mind.