I've always been against limited content that are not cosmetic. I don't have a problem with any micro-transactions as long as the game isn't built around them and doesn't affect the gaming experience. But I've always hated locked content. I mainly play games for the narrative. If you lock some parts it either ruins the experience or locked content doesn't matter at all. I'm cool with well done DLC mission packs. But pre-order bonus means the content is lost forever. It's better practice to simply give a pre-order discount rather than developing content just to be locked away.