Almost all of the heroic characters in this novel make brave sacrifices in order to make sure the main cast can save others. Note I don't say a lot about the actual wisdom of said sacrifices: many times the sacrifices the characters make aren't all that bright. Nevertheless, they make them. They're a survey corps ship, not really military, but they behave far better than the remaining members of UNIT in the previous book.
I have to say I'm getting really tired of Ace having emotional one-night stands with some soldier or other. It was all right for a book here or there, but it's getting a bit old. It would be one thing if she was just enjoying the connection physically, but it seems that every other book she's getting drawn to stay. Eventually, I'm sure this will end. Right now, it feels like a square on a New Adventures bingo card. Benny drinks, the Doctor is cryptic and creepy and enigmatic, Ace gets a soldier boy. I also thought the Epsilon Sigma character was too unbelievably dumb to be a Time Lord.
All of that said, I don't think I'll be reading this book again. It's like cotton candy, melting away. I can't remember almost any of the character names three days after finishing. I don't feel the need to go back and find out, either. I'm ready to move on.