OOPS, considering that Obambi is a Columbia U. and Harvard Law grad, and that he has a horde of professional speechwriters, it's BAD that none of them caught this mistake.
You say "nothing so satisfying AS....."
or you say "nothing MORE satisfying THAN......"
But you don't say "nothing SO satisfying THAN......"
Considering that this is supposed to be one of the "money shots" of the speech, that's poor drafting (unless Obambi simply mis-read what was in his prepared text.... then it's all on him).
"there is nothing so....................than giving our all to a difficult task."