Imho it's a very enjoyable expansion, maybe not the best one but an huge step forward from MOP and WOD.
Few things I dislike (not many):
- Warforged, Titanforged and especially Legendaries are a cancer for people who like to be competitive in raids. A good Leg vs a bad one makes an huge difference in terms of performance
- Artifact Power: too much grindy, it's endless and at some point you don't even feel progressing anymore. Just commited to farm it
- No Flying even after the first step of the achievement... not a core stuff but it's getting annoying
- PvP rng gear system must be reverted. I vote for the old honor/valor vendors
- Absolutely very alt unfriendly.