I wouldn't say arguably, I would say definitely that speed on the trigger was the defining trait of Ken Jennings previous domination and the key also to Brad Rutter's success. According to most accounts, the people who make it onto the TV stage on Jeopardy already have great knowledge. Most know the solution to most of the clues, but only one person gets to answer each time. What Ken Jennings says he did is that he would buzz in regardless of the question, based solely on if it was a category he knew because by the time it got to him he could figure it out. By focusing on being faster on the buzzer, he was able to not give his opponents even a chance to score. Essentially, the oters were reduced to only being able to answer when he got things wrong. The only person as fast as him was Brad Rutter, who defeated Jennings.
And this is exactly what Watson is doing to them now. Undoubtedly Ken and Brad know the answers, but Watson is simply ringing in first and freezing them out. Because it is a machine, it probably can time when to ring in more precisely than a human can. There's probably some light or signal that comes on once Alex finishes reading the question that lets people know it's time to buzz in. I'm guess the computer can react in milliseconds to that signal, while a human, for whatever reason, slight distraction, nerves, a cool breeze from the AC, might be slower by a few millisecond. The computer never has to worry about that stuff. That's how it is consistently beating them to the buzzer.
I'll say this about Final Jeopardy though, there are American cities named Toronto. I bet the computer mixed it up with the Canadian city facts.
But we got insight into how Watson bids on daily doubles and final Jeopardy. Watson is all strategic. He bet hard when he was close to open up a lead. Then when he had a lead, he bet small, to protect the lead.