"Welcome to our demo"
That wasn't a preview. Just like the Sacred Ashes trailer wasn't what actually happened in the DA:O game.
That's a
huuuge difference there. The Sacred Ashes trailer was meant to keep people interested and hyped for DA:O -- it was a prerendered cinematic. It was not meant to show what the game would be like at all. The Oblivion demo was meant to give an overview of what the game will be like (even if not exactly).
In the Oblivion demo, it talks about having true dynamic soft shadows, while showing off a much more uniform lighting and shadowing technique than what was given in the final game. Walls casting shadows, better defined shadows, shadows cast by more objects, etc. At the very least it's deceptive, even if not intentionally. It also talks about NPCs being able to decide what they want to do, and automatically picking up and using appropriate items in the environment to make it easier to do them, and being much more intricate in their tasks.. picking up food for the dog, putting it down on the floor for it to eat, and after the dog eats it, it gets energy boosts which you could see in it running around more often, which annoys the shop keeper and causes it to paralyze and flame the dog. Nothing like this happens in Oblivion, and in my experiences with modding, is simply not even possible without scripting (which was another point in the video, it saying those activities weren't scripted at all). It was meant to showcase what the game would have, and it didn't have them.
Something that interests me, though, is how the male Imperials were all voiced by the same guy that did them in Morrowind, even though they at least had some of the final voice work done already (Patrick Stewart's lines were done, and the female Imperial/Breton voices sound like the finalized stuff, too). Also, Baurus was an Imperial. Of course, that's not a complaint. Just an interesting side note.