I think the number of pirates was heavilly exagerated. The plaza was too small for 50,000 of them to have fallen there. But epic scare they get is epic.
So much for Ussop not being part of the weak crew anymore... he, Nami, Chopper and Pappagu hid inside the new weapon's control room. Or Ussop could at least be excused if it needs sniping.
Good old straw hat crew, bantering among them ignoring the enemy. Awesome.