I was fortunate enough to get 45 minutes in of Guild Wars 2 during PAX East, and have some comments on the demo. I'll start by saying it was great fun, because it was. I am a big fan of the original Guild Wars, and GW2 does a good job as a successor. My thoughts on the demo, as well as some footage of mine and another's demo, follow after the jump.
I chose to play as a Charr Guardian. I started at level 27 in the Gendaran Fields. I was able to capture most of the Guardian traits (there were some that I didn't realize until I re-watched the footage that I missed), and I think I got all the skills. From there, I just ran around the map exploring everywhere and killing stuff.
The Guardian is marketed as an area control specialist. If I'd had more time to experience the combat style of that profession, then I probably could have been okay at controlling area. In fact, KOTH is my favorite Team Fortress 2 gamemode, so I'm sure I would have been great at controlling areas.
However, what I found as the Guardian is that no matter how much Arenanet denies it, it makes an effective tank. It is surely possible that the Warrior could tank equally well, but I found that with the Guardian's heal spell (which makes it block attacks while it heals), and its Aegis and Justice boons, the Guardian is able to keep up a good amount of health. Also, the Mace's primary attack (1-slot) deals damage and gives health back in return.
For offense, I found the Mace and Torch the most effective. The Mace for the skill described above, as well as it's second skill which was essentially an area-of-effect slam. This slam produces a symbol, but I didn't really care about that symbol's effect. The Torch proved to me how effective fire is. Its two skills both deal with burning. One of them unleashes a cone of fire, which seemed to deal more than 50% damage to any enemy I used it against. That led me to the conclusion that burning and fire damage will once again be extremely effective.
As for the Guardian's utility skills: I didn't use them too much. The heal was nice. I set one of my utility skills to "Retreat" as I thought it gave me a speedboost (Swiftness) to help me explore the map. However, if you have Swiftness on you, your character has to be in combat mode (which is like walking), so Swiftness seemed to just make the character go on a slow run. Letting the character go out of combat mode to move around was the fastest method of travel, it seemed (letting the Charr get onto all fours). So this likely sees an end to the famous Runner. If no one can run faster than the standard run speed, it makes no sense to pay someone to run you somewhere.
I tried to stay away from dynamic events, as I didn't want to waste all my time doing one thing. However, from what I saw and what I've seen of others' demos, the dynamic event system looks pretty dang awesome. You can be exploring and go wherever you want, and then something interesting might pop up. You can do it if you want, else you can feel free to just run away.
Guild Wars 2 looks awesome, and I cannot wait for its release later this year.