Flying is the best thing added to this game for a lot of people, there's no two ways about it. For the ones complaining about "diminishing world pvp and danger", here's a nice video to get you up to speed with reality as to how that works in classic TBC and how much players actually like it (hint: for the majority, not at all when it turns into a gank-fest that doesn't let you do anything). But hey, flying is killing all the amazeballs world pvp!
https://www.youtube.com/watch?v=Isv2UgW_iPs