Won't Watson have a significant advantage on the final Jeopardy question where time is not nearly as much of a factor? If it can just keep pace for most of the game and then bet it all on that last question, it should be no contest.
I'm usually able to read any given question in about a second. Granted, I used to practice speed-reading trivia questions for an hour or so per day (one of the leagues we competed in projected questions via powerpoint), but there's at least one reason most Jeopardy! contestants are able to buzz in almost immediately on most questions.