To fast to come out.
First off profession classes have been forgotten sorely. Unless you are a Jewel Crafter there isn't much for you. The point of going a specialty type crafter was totally forgotten.
Removal of racial class and mount restrictions removes from the flavor of creating your character.
Reducing the amount of levels a character requires to get their mount is a sore note to long time players who have work hard and long to get to where they are.
Leveling was hastened in Burning Crusade and slowed now because of too many complaints. This hurts once again long time player and now new players who are being left with the stigma "noob"
If asking a question in Trade you are bound now to be ridiculed for needing advice or help.
Gold seller have completely destroyed the bank economy. A new commer will not be able to compete with long time players who demand large quantities of gold for low level item.
Lastly the in game society's have grown to expect perfection from all people who wish to enter a dungeon or instance. To get the items required by these people to make your character able to join with them you first must enter the dungeons but you can not enter the dungeons unless you group. This is wrong. All players started the same at one point or another.
I would recommend any person who wishes to join World of Warcraft to play for the sake of playing a game. To wish to join to adventure and complete all of the game is long, expensive and at times very discouraging.