By large I think flying mounts has taken away most of the wonder of exploration in World of Warcraft. I recently reacquainted myself with the world of Azeroth, or to be more precise my adventure started in Pandaria and it started on foot with only my trusted sabretooth to keep me company on my journey. As every expansion to date, after flying was introduced, you have to get certified for flying in that area and that also requires max level for the expansion.
So as far as levelling is concerned you are forced to schlepp around on the ground like some commoner. But that was hardly a problem, max level was never a hard goal to reach and by the time you hit the level requirement you had enough gold to buy that oh so alluring licence. And that was probably the last time you saw any great part of the landmass from the ground, travel from that point on became a linear path from point A to point B and all you saw was blue sky and treetops.
Now when flying was first introduced you quickly realised that the world of Azeroth was never built to be experienced flying, what looked like a beautiful evocative tree from the ground was nothing more than a blur of lines and pixels from the air. Which is not surprising, why spend pixels on something that few would ever see. So flying never felt especially immersive or interesting, it was mainly a way to travel fast.
Pandaria was no exception to this, the landscape was beautiful, the music evocative and the time spent traveling added, not subtracted, to the experience of exploration and questing. But all along I could see the end goal, the licence at the end of the road that would make all these beautifully crafted pixels obsolete. If I was a designer working on World of Warcraft I would curse the day flying was implemented.
So it was with a sense of joy that I discovered that Warlords did not come with flying out of the box, yes the devs have said that it will be implemented in a later patch, but out of the gate the only way to get somewhere is by flightpath or ground travel.
And I think this is a calculated design idea, that by not including flying they are keeping the sense of immersion and wonder fresh, slowing people down to smell the roses and enjoy the game. Because here is the rub, in most MMOG and life for that matter, it is seldom the goal that is all that interesting it is the journey to it and what happens along the way. And altho this might seem like a stretch to compare, I would say that a World of Warcraft without flying is a far more interesting place than a World of Warcraft with it.