I only played a toon to lvl 10ish a few times. So my experience is limited.
pro: The game is totally beautiful. The scenery and character models are just gorgeous. The game plays just as smooth. Its like butter really. The animations look great, the UI is well done and easy to customize. It is extremely bug free for a game like this. I never once got stuck on terrain or had a glitch. The character customization is one of the strongest out there, really. You can make a toon that looks just like yourself, if you spend enough time. I liked the skill combo design and the response of the moves. There were some neat cut scenes that move along the story.
con: You have to PvE for 20+ lvls before you even will know if you like your class in PvP. (Other then duels) The PvE content seems very generic and linear. I didn't feel like there were any options to lvl other then move down the road to the next quest hub and do them. No choices to make for the most part. I can tell I would be bored playing through the first 20 lvls again, so I sure hope I pick a PvP class I gel with.
I don't think the game is anything like WAR. Yeah I guess the end games both involve large scale PvP, but what MMO doesn't have that now. WAR has 100% PvP leveling and scenarios from lvl1. Aion you got nothing but quest/kill grind till you eventually make it to the Abyss. WAR has TONS of options to PvE level with 3 distinct racial pairings. Aion you get the exact same thing for every class. WAR is gritty, dark, and full of war. Aion is pretty and colorful with animations that look smooth.
It is more like WoW then WAR but even then you cant compare it to any one game. It is certainly better then most F2P games out there, however there are some awesome F2P games out and on the way. Its just another MMO doing nothing that special but doing it all very well and bug free. It has a ton of hype from being announced like 8 years ago or something
OK that's it for now, kids screaming in background gotta run.