Most of the earlier reviews must have been written between levels 1-20
In World of Warcraft, and especially in its expansions, in no way was grinding more efficient than questing. (A case can be made for Frost Mages AOE grinding in Vanilla WoW, but not anymore) For those who may be new to MMO's, grinding means killing a mob(creature) around your level over and over again until you level. Aion, like WoW, implemented grinding into its questing. Now Aion, unlike WoW, simply ran out of quests to do and made grinding actually apart of the leveling, instead of making it optional or a way to get ahead til your next quest. Simply said, you get bored real easy.
Aion right into the game will look pretty gorgeous. There will be sweeping land-scapes as far as the eye can see. Only you can't get to a lot of them. Where in World of Warcraft, you could essentially get to where you wanted somehow, in Aion there is a this invisible wall that will block you from going where you wanted. This is especially disheartening given the beautiful wings we are given, but the places we are able to fly is limited.
PVP(Player vs. Player) is what draws a lot of people to MMO's. World of Warcraft PVP got it right. It gave classes counter-classes that would essentially have the advantage when they fought. Unfortunately for Aion, it gives Casters a very noticeable advantage over Melee classes in PVP. Melee classes just struggle to actually attack the casters, while the casters slow and blast away from a distance. This is especially bad in flight form. They blast away, and when they are going to run out of flight time, they simply go somewhere safe where you can't counter-attack.
Aion is a game that has major flaws that take away from what could have been a very satisfying experience. For a game that was released a year prior in Asian markets, Aion had plenty of time to fix things up a bit. If the game itself doesn't fizzle out quickly, there may still be hope in future content. Until then, Aion will continue to be a MMO that will not live up to the standards of World of Warcraft, which is why World of Warcraft will continue to dominate the MMO market until something (probably from Blizzard themselves) can make a world that not only looks good, but plays well also.