Judging a sermon based on audience reception and response is not the best measure of its value/effectiveness. The thrust of the quote is most certainly - though innocuous at the same time - opinion, but carries a measure of truth, that being, a sermon that elicits praises for the speaker may in fact not be the best sermon. With that said, talking to one another after the sermon - about the sermon, if well received - is wholesome and indicative, usually, of a sermon well-preached. Much more could be said, but the quote is a subjective estimation of the benchmark for sermon value. The measure of a good sermon, ultimately, is not seen in hearer response but in its faithfulness to the Word.