GameSpot have been playing the second BioShock demo at X06 which is titled "Hunting the Big Daddy"

There's lots of new info on various plasmid powers, as well as a couple of other cool abilities.

This is where the real trouble began. The dead body of the splicer attracted a little sister in search of adam. When the little sister arrived, the main character tried to get at her to get the precious adam, but as mentioned earlier, the little sisters don't go anywhere without the protection of a big daddy. In this case, the big daddy grabbed the little sister and put her out of harms way. It's an interesting, bizarre, and almost touching relationship between the hulking monstrosities and the tiny little girls. In fact, as the demo went on, we saw the big daddy put itself between danger and the little sister several times, and the protection of the little sister was clearly the only priority of the big daddy.