Opinion: Flying Mounts make the game less immersive.

A lot of the narration Blizzard uses for quests relies on players following a set path through a zone. This means that taking to the air and flying from point to point can take you out of the experience.

I leveled two characters in early access. The first, I just flew point to point, not taking in the world.

The second. I only used flight paths and ground mounts. While travel took much longer, I saw a world much more developed than I expected. It isnt an easy way to get around but it has its charms.

If you are just starting the expansion today... maybe take the path less traveled.