Overall I liked the demo--it certainly got me very excited about the full game, which I did pre-order to get the signature edition.
There were a few things that seemed lacking in the art direction. I didn't really like the restyling of the darkspawn, I think they look like washed-out lizard people now, but it's a minor thing. The ogre still looked pretty cool, though. The areas around Lothering in the demo did seem kind of barren, and I'm not sure if that's just because it's the demo, or that's how the area has been redesigned, maybe to make it appear as if the darkspawn hack-and-slashed or burned their way to the village. Either way, we're not spending a lot of time there, so I can deal with it. I really liked what little of Hightown we saw in the demo, however, so I'm sure there's going to be some really cool scenery in the full game.
As for the voice acting--when I first learned that DA2 was going to be fully voiced, I was ecstatic. I played KOTOR and I really enjoyed it but I didn't like that the main character was not voiced. When I played DAO, I had the same feeling of, "Oh, I don't have a voice? :(" But eventually I was able to give my character a voice of her own and that worked pretty well. Still, it was hard at times to overcome the blank expression on the Warden's face at moments that were SURELY very passionate indeed. Either way, I did become accustomed to giving my character her own voice and I wasn't sure how well I would adjust to having that taken away.
I was pleasantly surprised on that front. I think being fully-voiced is great for DA2. I wasn't sure about the voices at first but female Hawke's voice has really grown on me, I absolutely love her so far. I only played one run through with male Hawke so I'm not sure how much I like his voice yet, but it didn't turn me off of playing him; that's a good start. I played through a couple of times on each class and picked different dialogue options each time and I thought it was kind of neat how my choices changed some of Hawke's future dialogue. I think it shows a nice consistency in the evolution of her character. After all, if I choose forceful, blunt dialogue options, it doesn't make sense for her to suddenly be wishy-washy in all of her other dialogue. Very cool, but it does mean I'll have to consider carefully what dialogue options I do pick so that I like what she says down the line!
Finally, the combat was both very different and refreshingly the same (I play on PC). I loved the closing attacks and the relative lack of shuffling that occurred. There was still a bit of it, especially when I had multiple melee characters all jockeying for position around a single enemy, but I remember my sword-and-shield Warden desperately trying to hack through Leliana or Alistair as they stood blithely between me and the darkspawn. This was a really awesome improvement.
I think I will again be playing a warrior and then a mage. I tried playing a rogue but the increased speed of the combat combined with the weird perspective changes anytime I switched characters or used backstab meant that I was quickly confused about my battlefield and it got a little annoying. Still, Varric was definitely cool with all that archery so I may just make a rogue anyway and go that route instead.
The combat probably is a little TOO fast-paced for my liking, because it seems too superhuman and unnatural, but on the other hand it's very impressive to me visually and frankly I constantly spammed Adrenaline Rush in ME2 and *that* is hardly human or natural either, haha.
tl;dr I liked the demo and I am really excited about this game