As far as I'm concerned, Dance could've been SoS levels of awesome had they done two very important things:
1) Trim the shit out of it-Let's face it, more than a few chapters in Dance could've been yanked out entirely. The Jaime chapter was just a lame-ass cliff-hanger that would've been much more effective had we gotten some follow-up in the same book, Tyrion's wacky slave adventures meander too much, Quenten Martell's stuff could've all been shoved into the chapter in which he bites it and bugger-all of value would be lost, and, of course, Dany's chapters needed to get chopped faster than Ned's head. Going over the same old shit chapter after chapter was just frustrating, I don't think anyone disagrees. I think they should've also taken out the Cersei material. But that leads up to the epilogue! Yes, which is why the last chapters of the book would consist of:
2) A bloody climax!-Bloat is one thing, but taking out both battles that had been signposted throughout the book was just criminal, in my opinion. Had George and the editors been more forceful in their editing, and gotten the book down to around the length of CoK, complete with the one-two punch of the battle of Winterfell and the battle at Meereen, we would've been looking at a goddamn masterpiece.
I don't think George has 'lost it'. Dance has some absolutely superb stuff in it, so I'm certainly hopeful for the future book(s). It's just that I get a bit miffed when I think of what could've been.