Some thoughts that came to mind, mostly having to do with the blitz tournament:
* Morozevich-Carlsen: Claim a draw! In an otherwise worse position, Magnus Carlsen repeated a position three times but didn't claim the draw. Alexander Morozevich promptly varied and obtained an advantage, and two moves later Carlsen lost on time. Yes, it was blitz, but I watched several players successfully claim a draw in the World Blitz Championship 2-3 days beforehand. It can be done.
* Hikaru Nakamura was the convincing winner of the blitz tournament, scoring an undefeated 7-2, but it didn't help him in round 1 of the main event - he was crushed by Shakhriyar Mamedyarov, and with the white pieces, too.
* Carlsen-Kramnik was interesting - both times! I was extremely impressed by both sides' play in the rook ending in the blitz, and intend a separate post about it soon.
* I don't remember if it was Andras Adorjan of "Black is OK!" fame, Mihail Suba, or someone else who joked that Black has the advantage or at least an advantage because he gets more information. White goes first, sure, but that first move represents a commitment. That's my thought about the way pairings were determined from the blitz. Nakamura won and chose his pairing number, Anand took second and chose his, Kramnik took third and chose his. Great? Not really. Carlsen chose fifth (behind Gelfand on tiebreaks) and picked a number that not only gave him five Whites in the tournament, but gave him White against all Nakamura, Anand and Kramnik. Whoops! Maybe a better way to reward rather than punish the winners is to have them bid secretly on what pairing number they'd like first, then second, third, etc., with the higher-placed finisher getting priority on his bid.
Someone might point out that Carlsen had no choice - he took the only remaining five-white pairing option left to him. That's true. What's really incredible is that Boris Gelfand didn't take that pairing number instead! Gelfand has Black against Nakamura, Anand and Kramnik, and only gets White against Carlsen. (Just speaking of the top five finishers, of course.) And going in the other direction, Nakamura starts and finishes with White, switching colors after every game. That's great in the abstract, but that doesn't count as much as who winds up with White and who with Black in a given round. Nakamura's reward for picking first? Black against Anand, Kramnik, Carlsen and world #4 Caruana. What a success! That isn't his fault; it's the fault of the system.
* Once a victim, always a victim: Sure as night follows day, Karjakin lost to Carlsen "on-demand", and Kramnik likewise lost to Karjakin. Time to consult a psychologist? (I know, in round 2 of the main event Karjakin managed to draw with Carlsen. But he did so with White, while making the game as "flat" as possible. It wasn't quite 1.e4 e6 2.d4 d5 3.exd5, but it felt like it.)
* Gelfand did okay, coming in fourth with a 50% score (though as noted above, he picked very, very, very badly when choosing a pairing number), but he could fairly easily have won the tournament. He was winning against Anand in round 1, but let him slip with a draw; likewise with Nakamura in round 2 and Kramnik in round 9. In round 7 it was even worse, as he lost a winning rook ending against Mamedyarov. In none of these cases were the wins based on obscure or deep factors; they were all issues of technique, where Gelfand has traditionally been considered quite strong. Maybe everyone is technically strong now, or perhaps his technique has slipped since his younger days. Whatever the case, he could easily have done better (though the value of that is unclear, as we've already mentioned).
In a way, it seems that Gelfand was unlucky. Indeed, as I think back about Gelfand's play, he's rarely lucky - that is, he rarely enjoys good luck. (By "good luck" I mean that a player is the recipient of an unforced error.) I suspect this is a question of style: players of a classical style tend to have fewer occasions where they can receive lucky breaks, while volatile "firebrands" create the sorts of chaos that make it possible. That doesn't mean a wilder style is better, except possibly when there is a 3-1-0 scoring system.