Well, I'm not very impressed with the guy I talked to at their Apple Care 1-800 number.
Called last Tuesday; explained I pre-ordered (3 iPhone 4S) via Sprint.com; it didn't say anything about AC+ only being available at checkout; Sprint's CSRs were idiots/didn't know what to do.
He checked withs someone, asked for my Apple ID and said he'd add AC+ to my ID; I said I'd ordered them on Sprint.com and they're not attached to my AID yet because I hadn't received them; he said it wouldn't be a problem; I explained that once received, they wouldn't all be until my AID; he said not a problem (at this point I realized I was talking to an idiot).
So he said he added it to my AID, asked for a CC number, never told me my total price, was about to hang up when I said, so you did this on all 3 phones, right? He was like uhhh, yeah.
No pending or actual changes on my AMEX, and no receipt, just a survey email.
Going to go to the Apple Store and get them to add it to all 3 lines. Already opened them, but I don't think that'll be a problem.