Most of us who will be buying Bioshock have probably already played the demo. But the extra preview of plasmids here will just whet your pallet more. There are a tonne of gameplay options here—and it should be clear by now that Bioshock will be a totally different experience for different players regardless of a lack of class system.
Notice when the developers discuss their goal to make plasmids feel genetic-driven as they stem from your character's hand. From the little I've seen of the game (and considering that few of us have truly known the sensation of mutating lightning DNA), it looks like they've succeeded.