One thing I liked was receiving experience for resurrecting other players. SO people wormed together more. I also liked how the personal story worked into the game. Champions online touched on that with a customized boss and minions, but GW2 seems to take it to an entire new level.
The reward system where your cut of the treasure is based on how much you help alone makes the game less frustrating. I can not tell you how many time I yelled at the screen in GW1 for players that coasted though a mission where every one else worked hard on. Or other games where greed let other players take your reward.
The new "No Trinity" is quite refreshing, and combat has the best strategy/tactics I have ever felt. For example - I was fighting and got lazy with a little button mashing which quickly got me into trouble. So I had to knock back the enemy, teleport out of range, then set up a doppelganger of myself to distract my enemy and attack it while I self healed and circled around to flack attack for increased damage. That is the excitement I want from an MMORPG battle.
Best yet not only is there no monthly fee, but items purchased in the store will only add color to game play and will not give you unfair advantages. In other words you can not buy a more powerful character.
I can't wait for the game to go live.
*note to players there is a stress test May 14th.