As other have said I preorder from Amazon, and only Amazon.
No tax and free ship, and a price discount on games not even out yet? Can't beat that.
Outside of the Amazon thing, I preorder for three main reasons.
- It's a game I HAVE to play the moment it's released. These games are rare, but everyone has some 'ZOMG I have to play this the first moment I can' games.
- It's a niche game that I feel will be in short supply, and may quickly dissapear as soon as it's released. I like to support small developers/publishers that make games outside of the ordinary. Companies like Atlus, and NIS.
- There's some preorder shwag I want. - This is not reason enough, I still have to want the actual game, but preorder bonus' can get me to bite on a game that I may normally have waited for a price break on.