I just listened to a post race interview with Bolt.
He says he was 100% ready to go, despite all of the pre-race chatter about his pulled hamstring and other things he might have pulled too much. I think he was being humble and did not want to use an excuse as to why he did not set a new world record.
If you watch closely, he looked very awkward, and somewhat pained in his first 10 meters. (For my American friends, that is about 10.5 yards).
Those of us who watched in anticipation of Bolt setting a new world record need to be satiated that we just watched the second fastest 100 meters ever run by a human bean.