I hate to say "I told you so" but I predicted all this months ago when the upgrade was first announced with the October 21st date. Computer upgrades NEVER go as planned. Not at Disney and not anywhere else. There should be specific steps followed in a logical order and, unfortunately, the steps at the end of the process are the ones that will get skipped if a deadline needs to be made. And those steps are the final testing and quality assurance that the product to going to be running as expected. Which causes the system to "crash". I live with a man who is that last person on the line and it's not pretty when he doesn't get the time he needs to make sure the product is ready to go. In a perfect world, the problems he finds in the last step should be fixed before the product gets online. But that doesn't happen in about 99.9% of the time. Because of the deadline date.
Trust me, take a deadline date being moved back several times over having the system not be ready to go.