Having recieved DA2 early for some reason and played for a while now I have to say everything about it's perfect, the new graphics engine, the linear story aspect which you change drastically, the controls, the combat, everything.
Every other review comments about the demo, DON'T DO THAT! The demo to this is dumbed down and missing a lot out, (class trees, characters, abilities, fights, scenes, dialogue options, customization) The demo is basically nothing like the main game, so don't bother comparing the two.
The best thing so far for me has to be the story, which is epic, allowing you to live 10 years in the life of Hawke, who has to become the champion of Kirkwall, battling demons, darkspawn and encountering many DA:O staples, (Alistair and your character return if they were made king and queen, , Flemeth, Anders, Wynne's funeral is in the game etc.)
The character models are now also amazing, in Origins only dwarves looked different, now elves are taller than humans and look drastically different, humans look beautiful and dwarves just look like little humans, without long hair and facial hair littering the place.
The new speech system meanwhile is amazing, my only gripe is it shows what your chosen action will do, which is a bit silly, but does help a lot if you want a good char overall. Also, the conversations work a lot better, as because your char can talk a lot more emotion is shown and better voice acting has been employed, no Z-Grade acting here, it's all A-Grade, one actress whose A-Grade and voices many games is back here, but I shan't say who, (Morrigan ;))
Finally, the longevity, the game is very long, very interesting and doesn't feel like a Mass Effect clone as much as Origins did, in the end i'd suggest buying this, it's amazing, the demo is nowhere near as good as the main game! TBH, the demo is rubbish