As you know, Blizzard announced that you can now pre-order Warlords of Draenor now for €45 (or €60 for the deluxe version, which includes a mount and a pet). Blizzard say they'll deliver "on or before 20/12/2014", so why would anyone bother to pre-order now? Because of the free Level 90 Character Boost. Is your raid short of a particular role? Order Warlords of Draenor today, and you can probably have your new level 90 raid-ready in a week's time. I'm considering it to solve Paoquan's dilemma, and get a tank/healer for our raids.
Wilhelm Arcturus has a list of what you get with your insta-90.