Gameplay seems hardly changed at all, which is a bummer, but it was a short clip, so hopefully there's a lot more to it.
I am in no way a "high level" Dark Souls player, but I could tell there were a lot of small, subtle changes to the nature of combat by the encounters they showed off. From mini-bosses being able to "block" backstabs to the movement speed of the player character being doubled (it seemed to be twice as fast anyhow), to swing animations being shorter and dodge rolls seemingly easier to pull off (and bloody quick, too). If anything it seems like Dark Souls 2 is going to be a faster playing game, but From Software isn't sacrificing the core nature of the combat in order to get there.
I didn't think the demo was mind blowing, but I was pretty happy when I saw it and the game looked, well, like Dark Souls. And the little touches like the dynamic camera angle during the walk on the bridge were nice. I don't think they'll do those little flourishes all the time, but it certainly seems like they're picking their spots for maximum effectiveness.
Also the UI is better in DS2 hands down. Then again it's not hard to beat the shit-flung UI of Dark Souls.
This ^ I will also point out that you have three item slots for weapons instead of two. You can also dual wield. There was really no point in DKS b/c you would use up more stamina dual wielding than if you just two handed one weapon or used a sword and shield. It also looks like you can equip more items in your item slot and see what's next in the slot. We saw no humanity at all and that would be really huge since that was a major gameplay feature of the last game. You can also use a bow while moving which again is HUGE new gameplay feature (which is already becoming a little controversial). It also looks like you can be locked on to an enemy and miss if you use the strong attack, again and big new gameplay feature. I don't see how anyone could watch that video and say there's no new gameplay features.