Seriously, when a server is moved, DNS entries in every nameserver on the internet must be updated. Some refresh pretty often but some are slow. This was actually a pretty fast propogation, and most people could access the new server in just a couple of hours. Some nameservers were slower, and that is what delays access to the new site for some people.

We could have used a technique called virtual redirection where a single system is "parked" on an address. The redirection system points first to the old system and then when the new one is made ready, the redirector switch is made. The switch is made in a single system instead of depending on all the individual domain name servers to be in sync (which they never are). That would prevent outages during the transition period where DNS propogates through the internet.

Moves are pretty rare, and there probably will be no need for another system. If not, then there is no need for a parked virtual redirection system. That's why we just basically pulled the plug on the old system, and reconnected the new as fast as possible. It's depending on the DNS to sync up that's the nail-biter.