Matured gameplay mechanics combined with immersive experience, incredible depth not see in any other MMO.
But with all the pros, there are some cons to balance things out.
1. There's a considerable amount of exp grinding and before you do that you have to form a party of usually 6 (depending on how tough the mobs are) but SE has made considerable changes to alleviate this through increase in exp gain, exp bonus items and better weapons/armor/abilities to defeat mobs faster. However, ultimately it's down to the individual's patience level.
2. Game is heavily focused on teamwork, usually requiring many end game content requiring 12-64 players.
3. Initiially ackward keyboard layout (layout remapable) but remedied via using a gamepad such as a PS2 controller connected to a Soyo Group's KiKy X-Series USB connector.