Aside from the new engine, from what i saw the trailer shows:
- swimming & diving (underwater areas)
- new really large creatures to fight (including a big ass dragon)
- seasons in all areas including capitols
- player housing (including custom furniture) next to capitols
- some kind of black-board system
- new travel system via boat (water & air), probably addition to flight master
- player mounts with option to carry another player with you as well
- feature to knockdown/tame wild animals and ride those
- new weapons/spells
- crossbows
- a Templar transforming his shield into a grappling-hook-hand
- Spiritmaster fighting on the back of a raptor
- the summoning of a huuuge mountain like giant
- a large battle between Elyos & Asmodians inside the asmo player housing area
Truely some cool stuff. Anything else you spotted, that i did miss?
Edit: You can download a HD version (448MB) of the trailer in .flv from NC korea here.