It's an absolutely awesome game on
many levels! I kid you not!
The level of detail in the graphics, sound and story is absolutely amazing, the gameplay is easy to pick up, and
the instancing outside of cities/towns/outposts eliminates much of the problems inherent in MMORPG's (though
Guild Wars isn't technically an MMORPG).
This game certainly has something for everyone. If you're only interested in the PvP, there are arenas for that. If you're more interested in the PvE (like me), you can still play it many ways: you can simply go out and kill enemy NPC's, or you can complete the many quests that refreshingly aren't all "kill someone/deliver something" type quests and that do flesh out the story and the world more. When you're ready, you can advance the overall story by completing particular missions in order - in this regard, it is (as a friend described the game) "a single-player game with an online twist". I would even favorably compare it to many single-player
and multiplayer RPG's on the market today (and considering it's about the same price - NO MONTHLY FEES - why the heck wouldn't I?

), one that updates online automatically.
When none of your friends are online, you can pick up NPC henchmen from cities/towns/outposts to help you on quests and missions. While usually not as strong as good player-characters, they're competent enough.
Of course, there's trading and other activities in the cities/towns/outposts. Though players don't craft items, NPC's can be paid to do so. You can also join Guilds with whom you can battle other Guilds in the arenas, chill with them at the Guild Hall (once the Guild leader buys one), and/or go on quests/missions together.
The world of Tyria is absolutely vast, with different environments clearly evident from one part of the world to the next. And it's not a resource-hog at all on the computer (unlike
Battlefield 2, another game I've been otherwise enjoying immensely lately).
And most importantly, the game has perhaps the most beautiful female characters I've ever seen in a videogame.
I hope that helped!
-G