Tiger was impressive yesterday (admittedly, I didn't see much of his round, other than his great low hook out of the rough, and his long putt that was headed to San Jose that found the cup).
However......
-- I think he had the advantage of starting on 9, and thus played a lot of golf before hitting the brutal first six holes. (So did half the field, and Tiger took advantage in ways that folks like his playing partners did not....just saying, though.)
-- Tiger in his pre-round press conference said anyone who played the first six holes even par would pick up a "boatland" of strokes on the field. To me, that's where Tiger made his round -- two birdies, one bogey, and three pars on the first six holes, that played as five of the six hardest holes yesterday:
http://www.usopen.com/en_US/scoring/cstats.html If he continues to play that well on holes 1-6 the rest of the way, he will be very difficult to catch. I'll be interested to see how he handles that stretch today right out of the gate.