The only new combat additions they've shown are martial artists (who seem like an evolution of the assassins in AC, they'll counter your counters and dodge your attacks) and bigger armoured guys (they seem a bit like Abramovicis and Titans morphed into one - no charging, but they have uncounterable attacks and you have to do an Ultra Stun on them to make them vulnerable and a Beatdown to break off their armour). You're also ranked after every fight, with what looks like the Challenge Room scoring system brought over into singleplayer. Other than that, combat looks exactly the same, but I'm sure there'll be new Quickfire Gadgets and special moves.
Investigations look really cool this time around. The batcomputer constructs an augmented reality simulation of the event that you can scrub back and forth through and walk around inside. through. The one shown in the demo is a chopper crash, where you have to rewind the explosion to see where the shrapnel goes, and then track it down in the real world.
I'm more excited for this game than anything else at the moment. The Arkham games are some of my favourites ever, and I absolutely loved IHUD so I can't wait to see how Origins turns out. I finally got my Campaign Gold achievement in AC a couple of weeks ago, so I'm 100% ready.