Despite a general dislike of Korean MMOs that I've cultivated over many years, I still feel like I gave Aion a very fair shot over multiple occasions. There was a part of me that really wanted to enjoy it, that really wanted it to be an MMO I could get into long-term. The extra effort to westernize the game for North American audiences is clear, and yet there was still enough of it that felt so very linear as to be a huge turn-off.
The graphics are crisp and detailed, and the character customization is surprisingly robust for a Korean MMO. The idea of altering body proportions is such a simple and effective way to create a more unique character, and yet so few MMOs implement it. World of Warcraft would be so much more visually appealing if we had more body proportion options, and yet Blizzard is so dead-set on maintaining their "visually distinct silhouettes" that there is little or no way to distinguish yourself from others.
But for every thing Aion did that appealed to me, it turned me off in some other way. One thing that annoyed me in the early beta and still annoyed me in the open beta were the voices. It's a great concept, attaching voice-over to spell casting, especially when you take into consideration that your character is probably muttering some sort of incantation to toss out that fireball. However in practice, when you're spamming said fireball in combat, and your dude is saying this phrase over, and over, and over again, you're going to reach the "oh my god shut up" cap pretty quickly. I must not have been the only one it was driving nuts, because I hear they've now added an option to disable voice on casting.
I'm also not a fan of class specialization happening at various intervals. Starting as a generic fighter, then choosing a more defined class, and then an even more defined class later on. I remember Everquest 2 did that, and at the end of the day you end up playing through the generic starting areas over and over again if you decide you don't like your class and want to try something different. It's a great concept, but I think it would be better implemented if they said "Ok, here is your class. This is your class for 50 levels. At 50 levels, you can specialize your class into one of two directions, but it will still very much be the class you chose to play."
It's not a horrible MMO by any stretch, but I think it's going to appeal to a narrower player-base than some western-developed games. It doesn't have the content (WoW) or the brand name (ToR) working in its favor. However if pretty-elfy characters with wings in ridiculously impractical and revealing armor is your thing, Aion has it in spades.