not much of a game-changer compared to some prior season finales. I had heard rumors we would be seeing Jacob pop up in the past of the major Lost characters and we got that. It seemed a little contrived to insert him so late in the game, though. Seeing Locke roll out of that box was not a huge surprise. I suspected that the Locke we saw on the island was something else -- he was too determined. Was he the smoke monster? If not, does the smoke monster really do the bidding of Jacob? Or the dark-haired man at the Black Rock beginning? Or is it the same as the dark-haired man?
My theory had expected the box to contain see something like another nuke to reactivate the Swan or Orchid and create another time shift to sync the 1977 and 2007 timelines. So that appears to be wrong. I did expect the nuke to get set off. It is unclear whether that changed history or not, or just enabled the oceanic 6 to get back to 2007 and reinforce the "whatever happened, happened" theory. It does seem almost certain that they will be coming back to 2007 since Jacob's last words were something like "they are coming..".
I expected the guitar case to have played a role in the finale, but it appears to be deferred another season, I also expected to see the return of Walt, since I have heard rumors of Walt playing a pivotal role in the series finale -- there is supposedly a secret scene they shot in season 2 to save for season 6 because they knew the actor would age too much in 5 years..