Both players took a long time to play "obvious" moves. (Typically, by this I mean something like a response to a forced move.)
Which specific moves do you mean?
I would have to rewatch the game, since the easily available record doesn't have the time it took them to make each move.
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.