The first time through I found it a little slow at the start, but once the Salvara game starts I was into it the rest of the way.
Also, I plan on getting Rhythm of War, but I'm thinking of not reading it until book 5 comes out. Usually I reread the series in preparation for the next book, and I think it makes more sense to wait for book 5 and then go through them all right after the other, since the first five books are meant to be sort of a complete story arc.