From a non-partisan observer....
Bush played to his strengths and made light of his weaknesses. He made a speech which was short on the fine detail, but broad enough to encompass the major themes and issues of the election campaign.
By making it 'folksy' he appealed to the ordinary man or woman in the street without running the risk of disengaging them with excessive detail. Rather than protraying himself as the man who is above you, he sought to give the impression of the man who stands by your side.
Simplicity was a theme which ran right through the speech. Clearly defined ideals, and contrasting with the Boston intellectual liberal image which the Republicans will use as a major campaign tool against Kerry. Bush sought to connect with Average America which is the vast bulk of the voting base. His humourous comment concerning use of language was precisely tailored to reinforce this.
The whole speech reinforced the message he wants to get across. "Agree with me or not, these are my clear principles" and that he does not surround these principles with clever Boston Liberal words and is therefore transparently trustworthy.
Again, this is a non-partisan view and a reading of the speech as I saw it.
Lead me not into temptation, I can find my own way there...