Well, I can say that I've never been involved in the construction of such a large building, but I'm surprised at the amount of time that they spend just digging into the ground. Ok, not really digging, but if you saw what we did everyday up close, it's obvious that there's a lot of stuff going on, but it's just not resulting in very gripping webcam footage.
If you notice, there's little green columns that are appearing on the right side of the lot in the front (closer to the top of the picture). Obviously, this has to do with laying down foundation into the landfill that is the Back Bay - to make sure that the Apple Store doesn't collapse, sending the Geniuses to a horrible death (imagine the headlines - it's bad enough with someone gets stuck in the 5th Ave Elevator). What you can't see is what these green things really are. Basically, it's a green pipe (looks like a large PVC pipe of sorts) pushed vertically into the ground with rebar located dead center surrounded by concrete.
Today, I took a closer look and on one of these - incomplete - they have a hose going into the ground, which drains the water into a nearby storm drain.
The Apple Store will easily be twice the height of the building that was there before and I'm sure that this requires a substantially stronger foundation than the building that was there before - not to mention the weight of all those Macs (how much will 1000 iPods and 1000 iPhones weigh - plus a 100 Mac Pros?). So in the process of placing these reinforced columns, it makes sense that controlling that water is pretty important.
So here's my theory: Just as the cooling of the exothermic process of forming concrete defined how rapidly the Hoover Dam could be built, the foundation work may be rate limited by the amount of water that they can pump out. Build too quickly on wet ground and the entire building might not stay up as you want. Maybe Apple's stock will hit $160, but they STILL can't bend the laws of physics.
Any large-building construction experts out there that can validate my theory?