Yukiko Amagi, just like Chie and Yosuke, has an evolved persona in Persona 4: The Golden. She can summon Sumeoomikami in the PlayStation Vita game.
Another key feature are motorcycles. At some point in the game you can acquire a bike license. Once you have obtain a license you can use bike attacks in battle. Persona 4: The Golden has new areas to explore, a neighboring town and sea area.
Index Corporation also hired animation studio Madhouse to make a new opening video. Famitsu has preview screenshots of it here.