Aion is remarkably like an MMO.
I don't much care for MMO's so I got bored around my mid 20's and quit. From what I've heard, the game becomes quite the grind later on down the road.
That said, the combat is pretty fun, and being able to fly is cool. It's also a gorgeous and yet very well-optimized game (in other words, will run decently well on second-rate hardware).
- J