I'm sure estimates will be available soon
I saw some blog comment from someone claiming to be (IIRC) an amateur 3-4 dan -- i.e., good enough to estimate this sort of thing pretty well -- reckoning probably 3.5 or 4.5 points in white's favour. That would be after the komi of 7.5 points given to white as compensation for moving second, or so I assume from the half-points in the figure. So that would correspond to black being ahead by 3-4 points before komi.
There have been a couple of brief discussions of this in the Open Thread, but it seems likely to generate more so here's a place for it.
The original paper in Nature about AlphaGo.
Google Asia Pacific blog, where results will be posted. DeepMind's YouTube channel, where the games are being live-streamed.
Discussion on Hacker News after AlphaGo's win of the first game.