Island people are in 2007. Jack, Kate, and Sawyer are in the same time as Sun, Richard and Lepidus(because the saw the firework the Others set off at the Temple). When Juliet set off the bomb the AU was created and they moved forward in time.

Personally I just loved being able to see some old characters like Boone and Charlie. And as someone who is a bit of a diehard Skater, I loved the elevator scene.

Idk. I loved the premiere. For me it was the perfect blend of characters, pathos, plot and mystery.