The game was great, combat system is really great and the dynamic quest system is pretty interesting, making it a sandbox-ish MMO where you have to explore and find out things to do yourself. For those who like a more structured quest system there's still the story quest but other than that it'll take some time to get used to the fact that the world doesn't revolve around you.
I have some minor gripe about the pacing though because most of the time I did some dynamic event, finished all the help quests and I'm still underleveled to go to the next area. It could be that I just missed some events but it could also be that the experience reward from those events are not significant enough. The event progress of some events are also too short so that we'll encounter the same event over and over again.
The story mode is the usual instanced stuff people usually find in other MMOs. The story itself is quite ok, although I find myself not quite engaged with the human and Norn storyline but very interested in the Charr storyline even though Charr is actually my last race of choice(I prefer Norn, Human and Sylvari).
Asura and Sylvari are still not available so i can't comment on any of those two and I actually managed to only try out a few classes, namely Necromancer, Warrior, Ranger and Guardian. I personally love the Necromancer because I can now be a Minionmancer without having to think too much on how to heal my minions. Ranger is also quite fun although the pet is a bit weak and unreliable. As for Warrior and Guardian I'll have to try it out again when the game is more optimized because in this beta weekend, getting into melee combat with my PC is ridiculous. Even at normal gameplay I only get around 20-30FPS and when plenty of people cast/use various abilities it'll crawl down to 15FPS or under. In a melee fight? it's unplayable.
ArenaNet does say that the game is unoptimized and will work that out for the release. I'm looking forward to the next beta weekend to try out the other classes especially the Engineer.
Short version: I'm impressed with GW2, I think the combat system is great, the dynamic quest is great but pacing needs some minor tweaking. Other than that, it's a game I'll gladly waste time on.
Check out some screens from the beta here: