I remembering preordering XCOM Enemy Unknown and getting some ingame clothes,an art book, and a Xcom badge to sow into my clothes (I have never used it but it was still neat).
I presume you are an Aliens fan if you buy the game, so some fan servicey dlc is fine (to me at least). Anyway, this game sounds like it plays well and reviews should hit a few days before release and you can decide to keep your preorder or cancel it when the time comes.
I would honestly like to see more interesting pre order bonuses for games like this one that can be stand alone. I understand that some people hate preprder dlcs but to chastise people who buy them goes a bit too far to me, let them spend their money as they wish.