Wouldn't the surprise factor have been gone by the time he won the AO?
No. Was winning the 2011 Australian Open any more impressive than him winning the 2008 Australian Open?
Up until the end of 2010, the pattern of the Nadal vs. Djokovic rivalry was pretty clear. If Djokovic was to beat Nadal, it would be on hardcourt, in 2 straight sets and outside of a major. Any match at a major, or a close/epic match, Nadal always won. In 2011, bit by bit, the dynamic changed.
2011 Indian Wells final
Amazing first set by Nadal, reminiscent of his 2010 US Open form. Nadal's first serve percentage then collapses, allowing Djokovic to win the next 2 sets comfortably. This match broke a pattern from the past that any Djokovic wins over Nadal would always be straight set wins on hardcourt and never in a final.
2011 Miami final
Again, a very good first set by Nadal, and his form holds up pretty well throughout the match. However, another pattern from the past is broken, namely Nadal looking more fatigued in the latter stages of the third set while Djokovic looked fresh as a daisy. In the past, it had always been the other way round. In this match, Djokovic seemed both fitter and more calm at the crucial moments in the third set and takes the match. This match was vital in changing the whole dynamic of the Nadal vs. Djokovic rivalry in the next period. Nadal needed to win at least one of the Indian Wells or Miami finals.
2011 Madrid final
The best Nadal moment in this match was his tweener shot lob winner. Djokovic beats Nadal on clay for the first time, another pattern from the past broken, and does it pretty comfortably. Nadal just totally outplayed overall.
2011 Rome final
Nadal shows a lot more fire and determination in this match, but has lost that inner calmness that he has based his success on throughout his career. Djokovic, on the other hand, looks focused, calm, fit and lethal with his shot making ability. Although Nadal has shown much more fire and determination in this match, Djokovic still won comfortably because he stuck to his job brilliantly while Nadal didn't have that inner calmness that he needs to succeed at crucial moments.
2011 Wimbledon final
Up until Nadal served at 4-5 in the first set, I thought Nadal was playing the better tennis. Nadal then blew a 30-0 lead and it was all Djokovic until the end of the second set as the match threatened to turn into a rout, seeing Djokovic take a 6-4, 6-1 lead. Again, Nadal had shown complete lack of calmness at crucial moments while Djokovic was supremely professional in his job. In the third set, Nadal wakes up to the thrashing he's getting and throws caution to the wind, winning the third set 6-1. However, in the fourth set, all the lack of calmness at crucial moments came back to haunt Nadal again as Djokovic took the match.
2011 US Open final
Nadal, for the only time I know of in his career, won the pre-match coin toss and elected to serve first. Nadal was 2-0 up in both the first two sets but was unable to hold serve whenever he broke Djokovic, as Djokovic proceeded to punish Nadal's lacklustre serving and backhands with brutal efficiency. In fact, only once in the match did Nadal break Djokovic's serve and then hold his own serve straight after, and that was in the third set going from 2-3 to 4-3. In this match, I think Nadal's mentality in terms of keeping himself calm was all over the shop, arguably the worst I've ever seen from Nadal, although he fought like a demon, winning the third set on sheer willpower.