Source: Joystiq
Some tidbits;
The demo started peacefully enough, though, as Dovahkiin walked over to a grouping of incredibly detailed flowers, picked one and moved on. He stopped to show the audience a tumbling brook with beautifully rendered fish jumping their way upstream. We were also briefly treated to the third-person perspective in the game, which was a stunning improvement over past attempts at the option in Oblivion and Fallout 3. Instead of appearing to float over the ground, Dovahkiin actually looks as if he is firmly planted onto the earth.
The inventory system has also seen design improvements. Once pulled up, the players scrolls left for the map or right for items, and to view skills, you look up -- literally, into the heavens. Classic RPG skill trees have been replaced with constellations, with each representative of a different play-style and depicting a unique progression layout. The map is actually a zoomed-out look at the gameworld itself, rendered in 3D and incredibly detailed. For finding specific towns or mountains this is very helpful.
The size of Skyrim's gameworld is said to be comparable to Oblivion's, but each area is significantly more detailed and interactive.