the biggest challenge down there - renting the space. so far, no tenants (note my China post above as an exclusion).
you realize that this was tied into the Manhattan stadium deal. Bloomberg knows that not alot of firms want to rent space downtown anymore. where they really want to be is on the west side of manhattan. the west side development plan, of which the stadium was the central part, would have put alot of office space into that area. Sheldon Silver, NY assembly speaker - his district is lower manhattan. since he had a vote on the stadium and west side plan - he killed it, believing that this would "force" more tenants to look downtown.
in my opinion, it won't work. NYC will get the shaft at both ends - no development of the west side, no stadium, and replacement buildings at the WTC that have very low occupancy rates, especially at the start.
They could get tenants if someone finally stands up and fights the perceived market value.
But that is getting way off topic into pork and nonessential taxes and corruption.
Small businesses could fill space if rent wasn't so high.