Something I really like is that they are constantly adding new things to the world they call 'Lore'. Story, Weapons, Characters, locations etc. You also have the ability to chat with other users although the chat rules depend on the server you join. Speaking of other users, you can join parties and becomes friends with people. You also have your own Character Page.
When you start you will have 4 character classes to choose from: Warrior, Rogue, Mage and Priest. There will be more available later on. You can even customize the complete look of your character. Hair, eyes, skin colour, armour, weapons, hats, helmets...
You can get more classes later on and change any time you want as long as you're not in battle.
There are a large amount of Quests you can take part in. Most of these consist of killing a certain number of certain creatures, much like WoW and other MMO's. But when you have nothing else to play, this game should suffice.
There are rare item that wont be around forever. You can play on the side of Good or Evil in the battle against Chaos.
It's a pretty basic combat system. You start off with a standard attack and one other one that uses mana. As you level up you will learn more skills that will use mana.
No matter which class you choose, there isn't much difference. Sure, you have a Warrior which will be able to paralyze your enemy for a very brief moment (it stops it from attacking once) which differs from others such as Mage and Rogue. The second attack these classes start off with are very similar, Mage has a fireball which burns your opponent continuously for 10 seconds where as a Rogue can poison which does the same thing.
This game wont ever be called creative or intuitive, thats for sure. The sad/annoying thing is that is could easily be so much better. It could never be like Final Fantasy or anything but even with Flash they could improve it so much but they never will because like I said, it is aimed at a younger audience.
There is just something about it that I find pretty addictive.
While the game has it's own currency you get from defeating enemies and completing quests (you can also get experience from both) you can also pay real world money to become a Member which allows you access to more Weapons, Armour, Quests (classes, I think) and Locations. You can also buy AC coins which is another from of currency in the game used to buy things you otherwise could not.
AdventureQuest Worlds isn't going to suit everyone and you may get bored with it after only a few hours or maybe even less but if you are stuck on the computer and bored out of your mind, this should provide enough entertainment. Or you might be one of those people who become heavily addicted to this game.