Aion = Smoke and Mirror's designed to trick you into thinking its not a grind.
Its not that the game is bad, its just not great. Sadly I didn't get a chance to play the RvR aspects so I will omit that from my review. When I heard about it, the RvR aspects were what made me want to play the game. What made me leave the game was the ammount of work it took to get to RvRing.
If you're familiar with NCsoft and its history then you know about Lineage 1-2. Lineage is known as one of the most intense grind games of the decade and sadly Aion feels as though it should have been called Lineage 3. You will play through the first 10ish levels on a starter zone. It'll be fun and wonderful but sadly once you it the 10-20s you'll realize that all you do is quest, kill tons of mobs, and kill more to try and eck in a extra block of xp so you can level.
If you're a PvPer then Aion isn't for you. I say this because of the ammount of PvE you'll have to go through to get to PvP. Its sad really and though Warhammer Online has been bashed a ton I still feel that that is the best modern PvP release to date. The PvP just isn't their. To achieve the level you need to PvP you must invest a ton of time into a grind. So Aion really only calls out to PvEvPers (in that order).
Sadly the zone design is very weak. If you've played a free to play MMO (F2P) you'll note that many of the zones in those games feel like a path or road with monsters along it. You start at point A at lev 1 and end at point B lev 10. Then move on to the next zone and go from point C at 10, to point D at 20. Aion is just like this. I found myself wondering: "Why did I pay $59.99 for a game that feels like any average F2P import from asia?" I couldn't answer that question and thus the level/zone design helped lead to me cancelation of my account.
Sadly Aion is weak. Its held together by wonderful art concept but sadly these are just facades to make your mind wonder so that you don't realize how weak the game is. If you want a game with flight then I recomend City of Heroes or Champions Online. Both games have wonderful flight mechanics and are 10x better.