It was the best possible start for Levon Aronian, as he not only won game 1 of his six-game match with Vladimir Kramnik, he did so with the black pieces. Aronian played the Semi-Slav, but Kramnik declined the invitation for wild chess, opting instead for the solid Moscow Variation (5.Bg5 h6 6.Bxf6). The players followed the recent game Gunina-A. Muzychuk from the European Women's Championship, and the all-knowing commentators assumed that when Aronian played 16...Qe6 rather than Muzychuk's 16...Qd6 both players were still early in their preparation.
Surprisingly, this assumption was false. Aronian, who played the novelty, was unaware of the game and hadn't spent too much time on 11.Re1 lines in general. Kramnik did know the game, but in a big lapse had not investigated it too seriously or with an engine (but I repeat myself?) and was on his own after Aronian's new move.
Unluckily for Kramnik, Aronian's novelty - one mentioned beforehand in at least two e-sources (Chess Today and the Chess Evolution Weekly Newsletter) - not only took care of Black's problems, it gave some for White to solve. Kramnik spent more than 20 minutes trying to decide "which slightly worse position" to defend, and in the long run he failed to do so. First, while 24.g5 might have been alright, the plan behind it, to continue with 26.f4, was not, and after 26...Rb8! Black's advantage had grown to near-decisive proportions. The problem with Kramnik's plan was that although it led to some pawn exchanges, which are useful in principle, the resulting weakening of his king's position was both serious and chronic. By move 40, in mild time trouble and with a position that was almost surely losing in the long run, Kramnik's choice of 40.Rd7? lost immediately. After 40...g5! 41.Ng6 Bd6 White couldn't both save the knight and cope with the threat of 42...Bxh2+ 43.Kh1 Rf1#, so he gave up.
Aronian's play was very impressive, but unless Kramnik is in poor form he's sure to put up a better fight than he did today. He'd better do so tomorrow with the black pieces, as a 2-0 deficit in a 6-game match will be almost impossible to overcome.
Now for some links. The event website was linked above, and you can replay the live broadcast (complete with commentary by GM Yannick Pelletier and IM Werner Hug) on this page (look under "Latest Videos"). GM Arkadij Naiditsch supplied live commentary, and you can find my own analysis of the game here. (Update: GM Sergey Shipov's analysis is here. It's worth your time, as his work usually is, but it's funny that he too is a member of the "Wow, great prep by Aronian!" brigade.)