The audience was apparently rather small and composed largely of Bush supporters -- 50% of those who tuned in were Republicans, a much higher proportion than exists in the general population but similar to what Gallup has found in polling following other Bush speeches.
Overall, the sample of 323 speech watchers rated Bush's speech in positive terms -- with 46% describing their reaction as "very positive" and an additional 28% "somewhat positive." That is well below average when compared with other major speeches Bush has given, which have averaged a 60% very positive rating in similar flash polls. That includes a 67% very positive rating for the famous "Mission Accomplished" speech he gave aboard an aircraft carrier in May 2003, in which he declared the major fighting phase of the Iraq war to be over.
Unfortunately, they don't offer a breakdown of the numbers by party affiliation. Obviously a significant number of Repubs were unimpressed.
UPDATE: Crooks and Liars points out a tidbit that they say comes from Keith Olbermann-- Only 23 million saw [Bush's speech], down from 34.7 million for his Social Security speech. That's fewer than one in ten Americans, and since the polling data skewed Republican, it suggests that much of th audience was movement conservatives. And it was still a worse outcome than his usual pep rallies. Further evidence that his only supporters these days are the gullible and the brainwashed. Hopefully the right-wing pundits will keep shouting about what a fantastic speech it was, and provide even more evidence that they're nothing more than bootlicking sycophants. That isn't a traditional American value, as I see it.