The world's #1 and #2 players increased their rating edge over their closest competitors by starting the tournament with wins. Magnus Carlsen used Ulf Andersson's old anti-Hedgehog line to obtain a slight but persistent edge, and when Vugar Gashimov got mistakenly excited about his own tactical possibilities Carlsen won material and converted the winning opposite-colored bishop ending.
Levon Aronian defeated Sergey Karjakin with Black in a non-mainline Closed Ruy. The position became surprisingly complex in a hurry, and Aronian negotiated the complications better than his opponent.
Finally, Anish Giri won with the black pieces against Boris Gelfand in some kind of oddball Slav. Gelfand's pawn sac in the opening looked pretty interesting to me, and in return his bishop pair seemed to offer some chances. As things went, though, Giri was able to absorb the pressure a bit at a time, and finally went on to win a long double rook ending. The champion of Reggio Emilia has continued his winning ways!
The other four games were drawn, so Carlsen, Aronian and Giri lead the A group after the first round. In the B group, Harikrishna, l'Ami, Nyzhnyk and Lahno were the first-round winners, while I'll note that Timman drew with second seed and current European champion Potkin. Finally, top seeds Turov and Sadler led the pack in the C group, with Adhiban, Tikkanen and Goudriaan also winning.
There's lots of good coverage on the tournament site, while TWIC's report on the first round is also worth a look.
Here are the round 2 pairings for the A group: