Innovative ideas adding flight, but not enough substance in the end....
Pros - I found the graphics of the characters intricate and interesting, with some great armor and at least the ability to put new skins on it if you didnt like it. A great array of skill trees that led to complex battles. The flying element in the abyss once you got some real flight time made battles amazing for my cleric. Some great 1 on 1 battles that could last for minutes. Rifting was a interesting concept, essentially you could raid and reck havoc against the enemy (although to some degree glorified ganking). If you get in a great legion, there were some great world boss encounters. Probably best of all was it was a very polished game as far as glitches/imbalances as MMORPGs go at release.
Cons - The reason this game has already dropped off (well and got a bad GS score) is the purpose. Its supposed to be pvpve with pvp > pve. Furthermore, gear progression is the key to keep a MMORG progressing. The end game pvp gear was easier to get by pve, so while pvp ragged initially it died out quickly (as at higher ranks if you died you lose serious points toward pvp gear), so safety dictated start pveing). Fort battles are a fascinating idea but 200 vs 200 doesnt run well on most machines and its frequently just chaos. Another killer is that you can solo end game gear, basically with some time and money, and it is equal to the end game pve set from dark poeta (which is a pain to run and nothing ever drops) and just about as good as the highest pvp set. So bascially to sum up the pve kills the pvp and the solo set kills the pve. So at end game less and less peeps were interested in both pvp and pve they just soloed fortress guards all day long (which is the best way to get money, ap, exp) and soloed their end game set.
What aion needs is an end game instance that is challenging, requires more than 6 people and actually drops loot, which is what keeps a western audience interested in pve. If they want pvp gear and pvp to work, they need to severely decrease ap derived from pve, so your pvp gear is from actually pvping. Lastly I dont think that the solo set should have been so epic, it really nixed all end game content.
If they're able to add some serious end game content with this bent, aion has great potential and could add a point or maybe 2 on my scale. Any questions about the game, send me a line.