Ok, well I was down there yesterday, and there seemed to be A LOT of crew all working away although they aren't really visable from this perspective.
As for the elevator shaft being covered, my understanding is it has something to do with safety. I don't know if it is true, I know OSHA requires temporary railings on all balconies, so I could imagine some sort of cover being necessary for any shafts not currently in use. Either to prevent people or equipment from falling in, it makes sense to me.
While I was down there, I also talked with Jack, the sales representative. He said as of yesterday, they had no more of the smallest floor plan (plan F) available, but that they had "at least a couple" of each of the other floor plans. I agree however, that the pace will pick up much more rapidly when they get to the residential floors. At that point the construction becomes much more standardized, the floor plates get smaller, and the general arrangement gets more regular.