If it's anything like my previous preorders, they don't take the money until later, although I suspect it has to be there in the first place.
I hope you can preorder the 3G version tomorrow, don't particularly want to have to keep trolling their website waiting for the magic moment. Much rather get my order in 8am tomorrow morning, then forget about it (yeah right ), like my iPhone. Used the Apple store app last time, worked instantly, I was done by 0802. Couldn't access the store via Chrome or Safari till after 9am!