It was the clock tower that settled it. The images of rebels driving around the central square of Homs, its famous clocktower visible, confirmed they had taken the city. This meant they could now sever Damascus from the coastal regions, cutting the Assad regime off from the remaining pockets of support it had outside the capital. It was over.
Right now, the rebels are at Umayyad Square in central Damascus; they have taken control of the State TV while explosions and gunfire can be heard in some neighbourhoods of the capital. These are likely to be bouts of sporadic fighting as pro-Assad militias try to make it to the coast or the Lebanese border.