Hmm... Interesting. Any theories on why? I think I liked the third book the least.
One thing I liked about this was how when she met that one guy on his horse in the stream (I can't remember anyone's name right now), he was the very picture of a romance novel hero. Yet later she found out what was happening with him, and things did not go as they might have in a romance novel.
This may be a bit callous of me, but back when I heard that Lois was getting divorced, I worried that it would have an adverse affect on her writing the way Robert Asprin's divorce seemed to have on his (though that's actually a more complicated tale than I knew at the time). But it definitely didn't; instead, a pragmatic layer has been added to her characters' romances that makes them more believable and makes them ring true. She writes about real love, warts&all. Her characters come to life, and I really care about what happens to them.
Though, another reason I like this book a little more than Chalion is that the romance of the main character in Chalion feels kind of tacked on at the end. The powerful emotional core of Chalion did not involve the interaction of those two characters at all, so while I was happy that the main character got a romance angle in the end, it seemed not quite a natural outgrowth of the plot. The second book was much more satisfying in this sense.