I was at the same LittleBigPlanet 2 preview event as Guy Cocker, whose subsequent hands-on with the game is comprehensive. My brief contribution here is only to say I am super excited by:

1) Sackbots

Fully 'programmable', customisable non-player characters (see one to the right with Media Molecule's Mark Healey). Slap on a green skin, set behaviour to follow, clone a few dozen times and pow! Instant zombie horde.

2) Steam and Cake

One of the new game's themes, as found in the Victoria's Lab world mentioned in the preview. This is a mash-up of steampunk and Victorian tea parties - so an instant win, basically, with the Fluffy High-Tech theme (robots and bunnies) a close second.

3) Passion Pit

It's hard to imagine a better tune to accompany the reveal trailer than Passion Pit's Sleepyhead. It's exuberant, bubbly and charming, much like LittleBigPlanet itself. More of this and similar tracks in the soundtrack of the game proper, please.