http://youtu.be/SG_3R9BoVvg
Kerrigan's lost the extra appendages and, apart from some weird hair, looks relatively human now. According to the Heart of the Swarm lore panel at Blizzcon 2011, she doesn't remember her time as leader of the Zerg swarm well, but has a good idea of the destruction that the swarm caused during her reign. Her thirst for consuming worlds has been replaced by a less megolamanic lust for revenge. She'll be at the centre of the StarCraft 2: Heart of the Swarm single player campaign. See her in action on the Blizzcon StarCraft 2: Heart of the Swarm preview trailer above.