I think what's significant is not the number of Egyptians who made an appearance during the day, but the number of people who are staying overnight in the square. Where as protests usually taper off around sundown, there were thousands still there about an hour ago- presumably there to stay. The sit-in aspect to protests today is what's strategically important, and many activists were complaining that the event was inaccurately reported by the media as a "march" rather than its intended purpose. If Egyptians can sustain large numbers of people in Tahrir, they may gain some important leverage over the Supreme Council of Armed Forces on issues like trials for former regime members and the release of political prisoners.
UPDATE: It's Saturday, and thousands of protesters still control Tahrir. According to an Al Ahram Online report, "Tahrir Square is now completely occupied, and closed to traffic." What's more impressive, a list of common demands has emerged from the various political forces in the square, including:
- The immediate release of all civilians who have been sentenced by military courts and their retrial before civilian courts
- The establishment of a special court for implicated in the killing of protesters during the January 25 Revolution. All implicated police officers are to be suspended immediately.
- The sacking of the current minister of the interior and his replacement by a civilian appointee, and a full restructuring of the Ministry of Interior, placing it under judicial oversight.
- The sacking of the current prosecutor general
- Trials for Hosni Mubarak and members of his clique for crimes committed against the Egyptian people
- Annulment of the current budget and the drawing up of a new draft budget that responds to the basic demands of the nation’s poor
- Clear and open delineation of the prerogatives of the Supreme Council of the Armed Forces, ensuring its powers do not infringe on the powers and prerogatives of the cabinet