When I was able to order @ 3:00AM CST (I tried from 12:01 until then and it finally went through at that point), there were no options to add a line to a family plan and purchase the phone. You had to either upgrade an existing line (in my case, I don't have an upgrade available yet) or you had to open a completely new line (although you can add that line to your "account") and choose a plan starting at $69.99 again.
There were no options to bill it to my account. I do not have a spending limit account, my account is always current.
The reason I was saying it was a poor decision to do this right before telesales closed is exactly that. Nothing was working for a LOT of people, their entire site was down for hours and ordering was completely blind luck for some people. Not to mention I had to basically add $80+ to my bill every month to even order one, which is something I'm sure I will have to call and sit on the phone for an hour while they straighten it out.
Overall, not a pleasant experience. I also had to call to "validate" my order this morning. Here's to hoping this phone was worth a night's lost sleep and multiple headaches.