Quick thoughts, because I need to go back to playing:
The downleveling system is brilliant. You can run around a level 5 area at level 10, still get a challenge and get loot and XP appropriate for your level.
The artwork, environment, landscape, everything is this game is gorgeous. I've gotten killed more than once just wandering around appreciating the level of detail and polish that went into GW2. It's a work of art in it's own right.
Smoothest online launch I've ever been a part of. The trading is down right now and the servers are a bit laggy, but it's to be expected. It's still perfectly playable for me.
The combat really started to click for me around level 10, when you really have to start watching what your opponents are doing and paying attention to position.
The game is an explorers dream. Lots of hidden areas, vistas, points of interest, etc. I had a complete geek-out moment an hour ago when I was doing an event and suddenly realized that I recognized the landmark from the first game.
The personal story is interesting. I'm enjoying it, and the choices that I get to make. I hadn't expected to care much about the storyline, but now I find myself looking forward to the next part.