EA now confirms plans to release the playable demo for Dragon Age II on February 22, less than 24 hours after going to the trouble to cast doubt upon the evidence of their plans (though the demo is coming out one day sooner than the initial news indicated). This page on the Dragon Age Website offers details on the demo, which they say "represents just a small taste of what Dragon Age 2 has to offer." Here's a bit on the demo, including word on how it can unlock an item in the full game:

In the demo, players will venture through the game's prologue, choosing from three different character classes. They'll also learn more about Hawke and hone their skills and abilities that will make them the ultimate hero. After finishing the prologue, players will enter a key new location in the world of Dragon Age, Kirkwall, befriending Isabela, a romantic interest in the game who is also a deadly smuggler. Upon completion of the demo, players will unlock a special weapon, Hayder's Razor, an ancient dwarven blade which increases health, mana, and combat abilities, in the full release of Dragon Age 2.