Civilization will give enough enjoyment to justify it's price, of that I have no doubt. Further, this may be the best civilization of all time, based on the previews.
However, the Aztec thing is nonsensical to me and really, really will or make or break my decision. If there are 18 civs at release AND the Aztecs come either at release if you pre-ordered or for free later if you did not, I may still pre-buy.
However, if Aztecs are one of the 18 and they are holding them for ransom for three months unless you preorder I will not preorder: to me, it is rewarding terrible practices.
In general I like to see reviews before I buy, and usually that works out well.
Yeah if its 18+1 then there's nothing wrong with it, its an extra civ probably was going to end up as a paid DLC but given for free as a pre-order incentive. That's optimistic thinking though, the pessimistic view would be its 17+1 and Ed has said there will be 18 civs at release it feels extremely bad/desperate and I just hope that's not the case, it would be a terrible decision and absolutely not worth doing as it pisses off a lot of people, is it really worth the reputation hit?