I look at it this way - If your gonna buy Brink anyway, why not pre-order it? If the pre-order bonuses are exclusive, then you have something others don't. If they release them later, then whats it matter? You pre-ordered it anyway, and you'll have 1 less "pack" to download (or pay for). It's not pre-orders cost more than buying it after it releases.
I agree, I am probably going to be pre-ordering Brink because I am 99% sure I would buy Brink within a week of its release anyway, so why not have the extra goodies that comes with it?
I am fairly sure the items are exclusive, because I remember in one of the videos the guy was saying that they are symbols that you were one of the first players with the game.
Also the Steam Pre-Order thats PC correct? Which would mean you cannot get it unless you play on a PC?
Yes, Steam is PC only. However the preorder items it comes with (Spec ops bundle if I remember correctly) is also available from Walmart for people who pre-order the game.