It's dynamic, you wander into an area and simply join into the event taking place. You don't have to talk to an NPC or accept any quest to get involved, the events simply trigger (whether you're in the area or not) and you can join in or you can ignore it. GW2 offers multiple ways to complete an event, it isn't just "kill 10 rats"...etc. With that said, there are a couple of the typical MMO quests in GW2 but the main content is all of the dynamic variety.
TERA is really grabbing my interest, I'm now extremely tempted to pre-order so that I can continue my character. I'm level 11 and I just made it off the starter island and into the first city.
I actually died a couple of times as well which I really like. I'm playing on a 360 controller while laying down on my couch, it plays like an action game which is exactly what I want from an MMO. All of the quest text is skippable and instantly forgettable, so sitting on the couch detract from the experience. The combat is light years better and more enjoyable than Amalur, but in a huge persistent world. The scale of the environments in TERA is massive, perhaps not quite as grand as GW2 but still - these environments are huge and have outstanding art assets.
Bottom line - the character animations, the hack n' slash combat with no targetting attacks, the great graphics at 80fps, the non-existent latency, the huge and at times majestic environments... everything really took me by surprise. This fps also don't drop much in heavily populated city environments. I never once saw my fps dip below 40 in the cities, I believe the game runs on Unreal Engine 3.