I missed him linking with Messi, they were excellent last night. As for the defending, we were lucky to concede only 1 from his side of the pitch, he was out of position most of the game.
It's not always fun when he tries to dribble through every near striker. And sometimes he's too committed to tiki-taka, maybe more than Xavi himself. But yes, totally deserves the contract extension.
Koscielny? No for me. We have enough players to score our share of own goals. Plus he cracks under pressure, Mertesacker is the one who makes Koscielny look good.
Vidic is just a worse version of the current Puyol. Injured mostly all season plus bad marking and ball playing skills (right now, he used to be a beast no doubt about that). The only good he has now is the aerial abilities.