For me it's between Button, Hamilton, di Resta and Buemi and Ricciardo for the following reasons:
Button - Solid race with good pace throughout. Won the race with a bit of luck and correct strategy decisions which he may or may not have made. I feel like Hamilton lost the race rather than he won it which is why I'm struggling to vote for him, although I probably should.
Hamilton - Where do I start? You make your own luck I guess but this year he has just been Mr. Unlucky. Only just missed out on pole again yesterday and today he was heading towards his 3rd win of the season. As usual he had some great battles from keeping Button behind him at the start to getting past Webber for 4th at the end. He was also the fastest driver on the track in the tricky conditions at the start of the race. I'm a Hamilton fan so my heart says to vote for him, but you can't just ignore everything that happened with two incorrect tyre calls and a drive through. He has a part to play in these decisions.
di Resta - Didn't really see much of him in the race feed but a great result to finish first in "Class B" and get his season back on track after some bad luck and several broken noses in the past few races.
Buemi - Again, didn't see much of him but to start from basically dead last and come through to finish 8th in what is probably the slowest car excluding Lotus, HRT and Virgin is a great effort mirroring similar results by Alguersuari earlier this year.
Ricciardo - Beat Liuzzi in only his third GP, a great achievement considering he's had no previous experience with the car.
I'm going to have to think about this one for a while before voting...