Actually, what you see on yours is quite normal out of the box -- as I mentioned, pretty much every one I've seen starting with the first generation powerbook G4 aluminium has that issue to a certain degree. If you remove the back metal display cover, you'd see that it's not really a problem of the aluminium bending out over the the plastic; it's more as though the plastic wasn't moulded 100% correctly to fit the aluminium. The design didn't allow for even the slightest misalignment and the assembly technique wasn't up to snuff for this design.
PS. Looking at your pictures, I think yours is less warped than many others. Also, if you just don't shine a light straight on the area where the thin edge of the aluminium 'protrudes', you won't notice it. Not that that's an ideal solution, but maybe it will allow you to forget about it?