Funny you should mention that.
I pre-ordered a couple of 'Comedian Joker' figures on the GameStop site about a month and half ago. Then late last week they became listed as "in stock" on the site and ready for immediate shipping, but my pre-order still said "awaiting item availability". Then a fellow Fwoosher posted that he ordered that same figure from GameStop yesterday and it already shipped. I checked my pre-order and mine were still sitting unshipped and "awaiting availability". So I cancelled my PO and reordered them. Hopefully they will ship tomorrow.
So that's how reliable GameStop is with pre-orders. They apparently ignore them in favor of new orders.
Hope that answered your question.