OK so I read it. It was OK but by far the worst of the series so far. Why on earth did Martin choose to make Cersei such a major character? She's awful, intensely unlikeable, and tremendously irritating. It didn't help the book was bloated and aimless with little real plot development and unnecessarily convoluted minor subplots and squabbles. I really enjoyed the segments in the Iron Isles and in Dorne and I liked Arya's chapters. Sam's felt completely pointless. Sansa's as well. Brienne's painted a vivid, grim picture of a land ravaged by war - I got a very Thirty Years War vibe from her wanderings. That vibe carries through a lot of the book actually, with roving bands of outlaws and deserters from the war, ravaged and pillaged villages, and religious fanatics vying for power. I didn't necessarily miss the characters that were left out but I also didn't see why Martin had to break the book into two parts - there was so much superfluous nonsense in this one that it probably could have been downsized significantly and combined with book 5 (also downsized, since from what I've heard it suffers from a similar set of problems) resulting in a book roughly the length of Storm of Swords, maybe a bit longer. There's really that much filler. Still, I'm ultimately glad I read it. Despite how little I care for some of the characters featured here, I like Martin's world too damn much to hate this even if it did test my patience.
EDIT: I forgot about Jamie! I liked his chapters. It's cool to see how he's developing from a heartless villain into something much more complicated. Almost, dare I say it, a good(ish) guy? I didn't expect that to happen and I think a less ambitious writer would have sat back and let Jamie just be GoT Jamie for the whole series. Martin's sense of moral ambiguity and character development (except in Cersei's (very static) case) is rare. Anyway Jamie is one of the characters I most excited to see through the end of this series, if and when that ever happens.