I received my MacBook Pro 15" yesterday after ordering it on July 21, and it shipped with Lion preinstalled which I'm thrilled about. The only change I made to my laptop was upgrading to a high resolution glossy display, and as such it didn't ship until Sunday.
Since my order wasn't that much different than the stock 2.2 GHz model, my guess is any change you make to your order to make it "custom" and will lead to Lion being preinstalled.