Robert and Liviu over at Fantasy Book Critic have posted their thoughts on Midwinter, and both gave it high marks.
Robert liked it in spite of a few issues. He was not sold on the interlude entitled "Conversations with the High Priest of Ulet" which is an excerpt from abstruse, Socratic-style dialogue between two fictitious historical figures about the theological implications of magic. Go figure. But he did like the Thule Man. As one ought.
Liviu was more forgiving of the books shortcomings, though he looked askance at antagonist Purane-Es, calling him a "comic opera" villain. So fans of both opera buffa and epic fantasy will find cause to rejoice!
Edit: Liviu is a "he," not a "she." I don't know where I got it into my head to think otherwise.