I'm enjoying the hell out of it. Turn the graphics quality down to high, and there is not that much lag. I mean, there's still some, but unoptimized, that is to be expected. My issues with it so far:
1) Crafting is bugged...needs to update your crafting level a little better, and crafted blues are a joke compared to standard blues.
2) I feel dirty saying this, but too much loot (or too much time to salvage). I do like the way they have mobs drop the loot of their type, though. Wish they would have a little better boss variation, though...not much payoff for killing a boss, it feels like, as well.
3) Voice Chat - in a dungeon, it should not be distance based in your group. If I am kiting, I want to be able to talk to the group.
I'm only level 15 with 10 hours in the game so far, but I see a bunch of promise, and it's like instant gratification kick-starter for me.