In the first round three very interesting games and one quick draw were played. For round three it will be important to draw the right conclusions from the first round games. I would like to recommend the round one commentary on the official site. Here the analysis is very good. For example in the game Leko-Bareev Black had a chance to win at move 28:
Here 28..Ne4! was winning for Black. Instead, being in time trouble he played 28..g5? and lost a few moves later. The analysis from Chessbase doesn't mention this move, and in TWIC it is mentioned as interesting only.
Armed with this excellent analysis, we can make some thoughts about the round three games:
Aronian - Shirov
Shirov surprised (again) with the Queen's gambit accepted, which he hasn't played much recently, and then never the line played in the game with 1.d4 d5 2.c4 dx4 3.e4 e5.
Shirov later made an interesting exchange sacrifice with 15..Nxe4. Again I would like to recommend the analysis from the official site. They show some important improvements for Black, including 18..Ne5!? and 19..Bc3!? Shirov however didn't follow up correctly and later lost the game.
I think Aronian, being in the lead would switch to a safer line against the Queen's gambit accepted, should Shirov repeat it in game three, for example 3.Nf3 Nf6 4.e3.
Being a point down, Shirov could decide to play something more aggresive, for example his usual Slav, or spring another surprise (I am still waiting for a King's Indian). Or he could play the Queen's gambit accepted again, with two remaining White games in the second half of the match.
Leko - Bareev
Bareev played again the Caro-Kann, as he did against Polgar. Leko apparently does not fear Bareev's 17..Rd5 and played the main line with 1.e4 c6 2.d4 d5 3.Nc3 dxe4 4.Nxe4. Bareev however switched to 4..Nd7 here.
I think Leko will play the main line Caro-Kann again. As I said above, his position in the game apparently wasn't too great - but there are enough alternatives, including the common 13.b3 instead of 13.Re1. There are also many alternatives for Black available, giving Bareev the opportunity to play different from game one.
Grischuk - Rublevsky
Grischuk played an absolutely brilliant game in round one. Even the end position is fantastic and worth a picture:
White wins because of his pawn on b6. An instant classic.
What is worse for Rublevsky, White's play looked so strong that the setup chosen in the Scheveningen may very well be refuted by Grischuk's preparation.
I think Rublevsky should choose a different setup in the Scheveningen, or not transpose to the Scheveningen at all. After 1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 Nc6 5.Nc3 a6 6.Be2 Black does not have to play 6..d6 (Scheveningen), he can also play 6..Qc7 (Paulsen), or 6..Nge7 (Taimanov).
Kamsky - Gelfand
In game one Kamsky tried 6.a4 against Gelfand's Najdorf, but didn't pose any problems and the game was drawn after only 23 moves. I think Kamsky will play another surprise, not a main line, but I cannot possibly guess what.