The title doesn't work: a paladin is a warrior, albeit one without armor. Ista is certainly a force to be reckoned with, but a warrior? Nah.
Bujold takes a somewhat minor character from "The Curse of Chalion" and creates a story around her. It's not a stupid thing to do: Ista was enigmatic in the first book, and with a long history of madness and guilt, who could resist using her in another book? I disliked how down in the dumps Bujold made her-- didn't think it quite fit with the guilt she felt over her ancient murder/accident. She has a lot of guilt, you'd think she'd welcome any effort on the part of the gods to change that. To change anything about her current, ultra-boring life.
All the browbeating and general grumping about are finally done away with in the last 50 pages, but geez, it's just too late. 450 pages, lady! You could have done this story in 250 pages with no problem. It shocks me that it won the Hugo and the Nebula. "The Curse of Chalion" was so much the better book. I suppose that's like Whoopi Goldberg winning for "Ghost" instead of "The Long Walk Home."
I found the humor in the last 50 pages welcome, although I know others who were irritated by making a harsh situation comedic. Well, that's the Bastard for you, no?