From what I could tell, the marches did get more media coverage this time. The cable news channels aired stories. Newspapers ran articles and I hear that the Washington Post finally bumped an anti-war protest to front page above the fold.
Why? This increase in coverage is not due to the size of the demonstrations (which were smaller than previous ones) or the growth of the anti-war movements. There are two reasons. The obvious one is Cindy Sheehan who is a photogenic face of the anti-war movement and who was big news in August. Every revolution needs its symbol. The other reason is that most Americans are opposed to the war. This is why the Post is featuring anti-war news more prominently. That newspaper has long been pro-government and dismissive of dissent in the streets. But the widespread change in attitudes about Bush and the war make it safe for the mainstream media to be more friendly towards antiwar protesters.
They also don't have to worry about being upbraided by the right wing punditry. You all may have noticed how right wing flak about dissent being "un-american" get little traction these days. And those right-wing extremists who foam at the mouth about lefties being "traitors" are just crazy extremists.
Chuck