I wasn't totally shocked -- that was about the toughest first-round draw possible -- but still, well done Del Potro and commiserations to Djokovic. I suppose that this would have been his chance to complete the set of major victories and to see him breaking down at the end shows how much it really did mean to him.
I agree jim360 that it was a very tough first round draw, even for him. The Olympic gold is the one elusive thing that he really wants. He's got a bronze I believe.
The Murray brothers are out in the first round too. Quite a few unexpected results so far. The girls who beat the Williams sisters were playing very well, Venus wasn't.
No shock to me. Djokovic would have had to go into the tournament (and Wimbledon, where he was knocked out early) "clean". Drug testing is taken more seriously than in other major events. IMO he'll be back as good as ever for the US Open, where he can, possibly, expect to have an advantage.