Detailed PvP Introduction In Aion
In the Abyss, there are also Fortresses and Relics each side fights for control over in Aion. Relics have unique powers that, when used, affect all players of the controlling sides faction. These powers are impressive/useful enough that they can really play a factor in the outcome of battles, so it's in the interest of both factions to control as many relics as possible.
Fortresses have time-span's where they are seizable. You do this by laying siege to the fortress, breaching the outer door, and then killing a raid type boss that lies within the fortresses interior. There are also forcefield type generators in fortresses that prevent air raids, these are important to defenders because it creates a choke-point of defense. By taking out the shield generator the fortress can be breached from the air as well, which causes it to be intensely difficult to defend. Successful fortress sieges award medals, which are used to buy some of the best PvP Abyss gear. Owning a fortress grants the capturing Legion(guild) a large monetary value which basically simulates "taxes", as well as provides your faction with a local trading/crafting hub deep inside the Abyss. This is mportant because the game's fast travel system can be a real drain on your bank account. The reward system is good enough to drive the siege system continuously, which is a great thing.
As for the level grind, it's not too bad. Worse than some games, better than others. There are enough quests in the newer versions to take you to cap w/ a minimal amount of grinding. The Abyss + Rifts break up the grind pretty well by adding a nice random PvP encounters to the game. You are not terribly big on the PvE leveling grind "fun factor", as you have never played an MMO where you actually found that particularly interesting, but it is not horrible. Individual fights move a little slower than you would like (it takes to take down a single mob, not the speed of gameplay). You could find levels 1-25 to be pretty painful, not because they take a long time, but because it's all PvE and your characters skill-sets aren't fleshed out enough to really "enjoy" them yet.