Great win for Nadal. While not his best performance today, he did enough to win the TBs.
The question now is whether he will be physically and mentally fresh for the Open. There's a reason that ONLY Rafter and Roddick have ever done the Montreal-Cincy-UsOpen together. Law of averages does bound to catchup with everyone. From Nadal's perspective, he will hope it doesn't happen where it really matters - in the Open at NYC. I expect Djokovic and Murray to be fresh and rearing to go. I would still put them as the favorite, with Nadal very close second.
Does Nadal get to #2 for sure? If so, that's a huge advantage, since he avoids Djokovic until the final. Djokovic IMO is one player who got beat Nadal on a hardcourt, even if the Spaniard plays his best.
Finally, I don't think this is the best hardcourt tennis Nadal's ever played. That's a bit much. UsOpen 2010 and the fall season that year: Nadal served incredible (more variety, higher mph, higher peak speed), won more cheap points on serve, moved better and also played more offensively than he is now. Not to mention he was way quicker then.
Overall, UsOpen is going to be very interesting this year. Delpo, Isner, Berdych and Raonic can also make some noise and take out one of the big 4 potentially. Although the winner will likely be on of the top 3.