Despite the fact that Bush's speech received his worst ratings as President, and virtually all that watched it are Bush supporters, it seems to have helped in polling data released by Gallup. My guess is that it has more to do with the discussions surrounding the President's speech, rather than the actual speech itself, that helped improve people's outlook on Iraq. Bush's job was to simply make Iraq front-and-center in the national discussion for a while instead of hearing the daily death toll from the MSM. Captain Ed reports:

Gallup announced yesterday that it had taken a snap poll after the speech given by George Bush on the war in Iraq from Fort Bragg. The poll showed some movement bolstering support for the war. In fact, it showed Bush picking up ten points on whether we are winning in Iraq (up to 54%), twelve points on keeping troops in Iraq until the situation improves as opposed to setting an exit date for their evacuation (now at 70%/25%), and seven points on whether Bush has a clear plan for handling the war in Iraq (up to 63%/35%).

All of these gains were made, Gallup points out, despite the fact that the speech had the lowest ratings of any prime-time presidential address in Bush's terms of office. Only 23 million people watched the speech, and Gallup notes that most of them consisted of Bush supporters. CNN also reported on the low turnout for the speech