So, he (it?) won handily. But he did get some things wrong - some the sort of things you'd have thought he could look up easily (Serbia instead of Slovenia as the only former Yugoslav republic in the EU), and some just weirdly wrong ("Dorothy Parker" as the answer for "The New Yorker's 1959 review of this said in its brevity & clarity it is 'unlike most such manuals, a book as well as a tool'"???), though to be fair that was a daily double; his 14% confidence rating got it a "let's try" and wouldn't have been a ring-in level for a normal question. Still, I don't think a human would have said "Dorothy Parker" for "review of this" coupled with "manuals, a book".
It was interesting, too, to see the categories he wouldn't ring in on - the 'also on your computer keyboard' category, with things like 'abbreviation for Grand Prix autoracing' (F1 - Watson's best guess, not good enough to try, was 'gpc' at 57%); 'an additional section placed within the folds of a newspaper' (insert - Watson had that at 12%, behind broadsheet at 16%, neither good enough to ring in with); and 'football position that can be split or tight' Watson had "linebacker", at 20%, behind "fullback" at 13% and the right answer, "end", at 12%. And when he did ring in, (on the fourth question they tried, for $400) he said "Chemise" for "Shift" - got the "loose fitting dress" right but 'forgot' about the 'computer key' part of the question. The last one (proverbially where the heart is), was trickier for him - he had the proverb at number one - but the whole proverb, not just 'home' - but also had delete at 11% and encryption (the encryption key?) at 8%).
A classically structured question, 'A 15-ounce VO5 Moisture Milks conditioner from this manufacturer averages about a buck online' (who has any idea what it costs?) should have had the answer "Alberto", but Watson's best guess (at 40%), weirdly was "butter". Of course, he didn't ring in with that, because he knew it was wrong, but what a weird answer. Another was "white clothing" for "Wellingtons at Wimbledon", 20% (ahead of panties at 14% and boots at 10% so nothing would have been right).
Also, sometimes he was he was right but doubtful: the "buck or less" rap singer signed by Eminem was indeed Fifty Cent, but Watson only had 39% confidence.
But when his confidence was high, he could clearly ring in much faster. And he won. As Ken Jennings wrote on his Final answer screen: I for one welcome our new computer overlords...