Ross Douthat of The Atlantic put my disappointment into words:
The speech had good lines and good sections, but for the most part it felt surprisingly banal and jury-rigged, and it suffered throughout from a failure to cohere around any single theme or rhetorical style. There was a lot of liberal boilerplate (recruit an army of teachers, tax the rich, etc.) that could have fit easily into any Democratic acceptance speech of the last twenty years; there was a series of swings at John McCain that, while often effective, seemed more appropriate to a veep's speech than to an address by a Presidential nominee; and then there was a half-hearted attempt to return, in the speech's final third, to the themes of post-partisanship and national unity that defined his '04 convention speech. The whole thing felt schizophrenic - part Clintonian laundry-list, part McCain-bashing polemic, part "beyond red and blue" peroration - and watching it I was left with the impression that Obama would have been better off just sticking with the high-flown inspirational style that got him here, and waiting for the debates to recast himself as the meat-and-potatoes guy who can throw a punch and get down into the policy weeds. Hindsight is 20/20, of course, and you can see what Obama and his speechwriters were trying to do - namely, have the best of both worlds, by being soaring and substance-oriented, combative and post-partisan. But the substance was predictable, thin, and rife with pandering, the combativeness felt faintly inappropriate, and the speech didn't soar nearly as much as it should have. It was a historic evening, for Obama and for America, and there were moments that gave me shivers just watching on TV - but if you didn't go in sold on the Democratic nominee, I think it was ultimately something of a letdown.