In the marquee matchup of the day, Magnus Carlsen defeated Vladimir Kramnik. Paradoxically, the victory was both convincing and perplexing, reminding me of how people felt back in the Karpov era. With White in an English, Carlsen didn't seem to achieve anything at all by the time they left theory around move 19, but he started posing problems that Kramnik simply couldn't solve. When Kramnik finally resigned on move 43, his position was in ruins everywhere, and yet after the game neither play was really clear where Black had gone wrong.
The battle between Hikaru Nakamura and Ni Hua was a very different story. Ni Hua went very wrong early in the game, overlooking the nice but not terribly difficult shot 19.Ba5. After this he was lost, but from this point on he put up strong resistance. Nakamura missed or rejected several winning lines before the time control (with plenty of time on his clock), and that let his opponent escape with a very fortunate draw.
The other draw was much more normal, a good battle between Howell and Adams.
Finally, there was the horror show that was McShane-Short. On move 14, White reached a very, very slight edge in a typical Scotch ending. Over the next 12 moves, Black made several small pawn moves, and then nothing happened from move 26 until move 61. The players then swapped a pair of rooks and pawns, and then after another lull there was a bit more action. McShane never had more than that slight edge the whole time, but finally, on move 85, Short made a clear error. White won a pawn on move 97, and although the route to progress was already clear McShane waited until move 133 to put it into action. By move 147 the advantage was overwhelming enough that Short could have resigned, but he understandably kicked on a while longer, only giving up on move 163 after McShane prevented him from amusing the spectators in a king vs. king, bishop and knight ending. This monster game went almost eight hours, but in case you're wondering it's nowhere even close to a record. (That 269-move abomination can be found here, during the thankfully brief era when FIDE allowed a 100-move rule for R + B vs. R because there are several positions in that ending that can be won by force in more than 50 moves. [Never mind that they are rare and that even GMs can't always handle the ordinary, standard theoretical positions in that ending all that well.])
Carlsen and McShane therefore lead, and they play in the morning, with Carlsen having White. Other pairings: Kramnik - Ni Hua, Adams - Nakamura, and Short - Howell.
The games, with my comments, are here.