I'll get impressions out of the way first: It's faster and more brutal, less cerebral and more exaggerated. You might think that's because BioWare wants to make the game a little flashier and more accessible, and you'd be right in part. But Dragon Age 2's dark secret is that even if the action is a little more over-the-top and a lot darker, there's a real, solid, story-based justification for it.
As you know if you've been paying attention to the game, the sequel's story revolves around a character named Hawke, not the customized, silent Gray Warden protagonist of the first game. While you're still able to customize your appearance and your class, Dragon Age 2 consists of Hawke's story, not just one you're making up.
And here's the catch: Someone else is actually making it up. The main characters of Dragon Age 2 are actually Cassandra and Verik, two people ten years down the line from the first game, that have to save a world on the brink of war not by fighting their own battles, but by finding out just what Hawke's been up to since Dragon Age: Origins. In other words, the game is told in flashback, by a not-always reliable third party. Which means that if Hawke's story is flashier, grittier, or more fanciful than the first game, that's okay -- anything that might be a lie probably is. "We wanted to see what happened if a legend is exaggerated," said Laidlaw during the demonstration.
That doesn't mean that Dragon Age has lost its core RPG combat mechanic -- you can still pause the game and assign orders to your characters. But it does mean that Hawke can mow down baddies with just one whirlwhind ability, or that his mage cohort can summon a magic meteor storm with just the press of a button. Moves are gory and flashy, with limbs and blood flying everywhere after a big slash or a devastating spell.
"We wanted to see what happened if a legend is exaggerated."- lead designer Mike Laidlaw
It means that the pressure to tell a story moves from the dialogue tree to the narrative itself -- while there are still choices to be made, dialogue works much more like Mass Effect's dialogue wheel, and BioWare has even put icons in to match up with each dialogue choice. If you consider choosing a line that is more diplomatic, you'll see an olive branch icon before you choose it. But going with a line that will lead to a big fight will have a clenched fist icon instead.
And it means that after just a few minutes into the game, you can see a dragon swoop out of the sky, magically transform into a woman, and "she" can walk up to Hawke and company to slyly say, "Well, what have we here?" No, that might not be exactly how it happened, but the story you're playing is the story being told, not the story occurring in Ferelden.
Not much was revealed about the characters fighting with Hawke. He (or she) starts out with a human mage sidekick, and while there are some new tricks (mages can now get the "finishing move" cutscenes that are sometimes possible when downing a larger boss, and one dialog option allows you to send your companion in first, allowing them to direct the battle for once), characters control about the same. They do feel faster -- BioWare has decided to lose the "move queue" idea in favor of more responsive controls, so when you press a button, it feels like you're actually swinging a sword instead of just telling a character to swing the sword as soon as they can.
It's worth mentioning that Ferelden seems to have changed, too -- while the first game could be quite lush at times, this one is much more stark and barren. The enemies are darker in shade and slimmer than the first title, and the heroes are less shiny and more rugged. Of course, the demo only consisted of about ten minutes of gameplay (which, in Dragon Age time, is as good as nothing), but especially if it's representative of the larger game, we're in for a rougher ride.
That framed narrative is the key, however -- BioWare isn't just turning the sequel into "Dragon Effect," it's actually baking a story into the game that allows the developers to go bigger cinematically and thematically. We don't yet know how Hawke's story will play out -- Laidlaw promised that players would make decisions that show how "the Chantry's fallen to pieces" and the world is brought to war. But however it's done, we'll be hearing about it from an NPC as we play.