A few off top of my head:
Dynamic snow drifts
Killing the mill means less arrows in the shops
In Game economy
Working at a mill means a more wealthy village = better gear = less prices ect.
They made out you could chop down trees.
Duel wielding magic was the shizz (its really not and doesnt serve as much a purpose as they made out)
And finally, the biggest lie of them all : New engine.
Yeah, the dynamic snow is BS. But i'm pretty sure they never said you could chop down trees. They did state many times that they don't do very much deformable terrain

I remember when Todd showed the E3 demo, Hod said "bring me all the wood you can chop", and i think people misunderstood it. Correct me if i'm wrong though.
About the engine. I think it is to some extent "new", since i cannot notice any Gamebryo trademarks in it, aside from bugginess and general performance. But it might be just heavily modded Gamebryo, hard to tell. Animations look new, graphics are better, everything is basically turned up. Like i said, hard to tell.