The blogosphere agrees that Obama's speech was a B+ at best. (I recommend Packer and the TNR staff.) I tend to agree with this as an absolute assessment, but I do think it's better than the post-Iowa fluff or the much-praised Jefferson-Jackson dinner speech that jump-started his campaign in late 2007. As Noam Scheiber (TNR) says, the inaugural speech had a coherent historical framework, viz. that the past eight years were an unfortunate detour from the main sequence of American history, and that "America is back." The implication here is something like "for eight years, we were the kind of country that waterboards innocent people, but now we are the kind of country that elects minorities to high office." Obviously this wasn't something Obama could say, but surely it was at the back of everybody's mind.
Packer is right, too, that Obama is not a natural phrasemaker, which showed; the antitheses were less than taut, the metaphors more than a little tired. However, the first five minutes were pleasantly and unexpectedly stern, and the speech was essentially perfect up through "their full measure of happiness" (a felicitous phrase). The stuff about the Puritans was structurally necessary to set up the Washington-themed close, but came across as gaudy and not deeply felt. The policy stuff was a mixed bag; on the one hand I heard a lot of things I liked, but there was also a lot of inappropriate blather about small government, and a wholly preposterous remark about harnessing the sun and the moon and the fixed stars to run our SUVs. (He did this before at the DNC -- he should've learned from that.) The bit about foreign policy was sound and well-said, and had to be said. However, the call to service was boring and overlong, and things only drifted back into orbit a couple of minutes later with the statement that "what is demanded of us is a return to these truths" (a sentence that would've been at home anywhere in the speech). The best line was the single, beautifully timed reminder that he was black; the GW stuff was part of the structural "let's get back to the Founders" message, but could've been better written. The close, as I said, was a deeply unimpressive descent into fustian.
This is all beside the point; there was so much historical weight behind everything he said that the quality of the speech hardly mattered. And this is partly why you realized, two words into Elizabeth Alexander's (ultimately not very good) poem, that it would be anticlimatic regardless of its merits. Of course, it was impossibly dumb to write a poem for Obama's inauguration that ignored everything that was special about it, and that would have read equally well at Bill Clinton's, or Bush's, inaugural.
Incidentally, I find it extremely annoying that the only available transcript of the poem is missing the linebreaks that are obviously there in the original (you can tell from the scansion, it's in loose pentameter).
Obama's speech did, however, remind me of this:
And now in age I bud again,
After so many deaths I live and write;
I once more smell the dew and rain,
And relish versing: O my onely light,
It cannot be
That I am he
On whom thy tempests fell all night.