At this time, there are no numbers about turn-out at this rally. However, it seemed (because there was no Reflecting Pool to get in the way) a lot more well-attended than that one held at the end of August. The numbers will likely come out later.
I really thought that the closing statement by John Stewart was really quite powerful -- and I'll try to link to it, if one gets onto YouTube (and is relatively stable there, too).
Webcams from the Washington Monument appear (at this time) to be disabled, so I will just share this shot taken from the traffic cam at Pennsylvania Ave and 7th St of people beginning to leave the rally:
Now, that's a lot of people. I really do wish that I was able to go.
UPDATE (November 2, 2010): According to CBS, the rally attracted roughly 215,000 people. This was much more than the estimated 150,000 expected attendees that Comedy Central used when ordering the port-a-johns, and much, much more than the CBS estimate of Beck's Rally to Restore Honor of 87,000.
To the left are side-by-side photos from the CBS website contrasting what the numbers mean. As you can tell, the Beck rally was held in front of the Lincoln Memorial, complete with the Reflecting Pool, which meant that it had roughly 3/4 the space as the Stewart rally would have. (Which means that -- if the Beck rally was able to fit an additional amount of people packed to the same density as people found on either side of the pool, there would have been roughly 116,000.) In addition, the Beck rally has a lot of green visible in between crowd members, while there is much less green visible in the Stewart rally. (Let's estimate that the Stewart rally had roughly twice the density of the Beck rally, so if Beck was able to pack in the same density of people in the same length of the Mall -- including having people in the area of the Reflecting Pool -- there would have been roughly 232,000; which is within the same range of people as at Stewart's rally.) Therefore, while both Beck's and Stewart's rallies appeared to peter out at roughly the same place (the Washington Memorial), it doesn't mean that the numbers were anywhere close, since Beck's rally surrounded the Reflecting Pool, and the Beck ralliers were not packed in as tightly.