Was not a fan, but Ive tried to understand it and like it more the past few days.
I wish the following were true, which would make me like the episode even more:
1) Jacob knew the light could never leave the island and he would protect that for a long time, therefore that is why he threw his brother into the cave. The episode made us believe he threw him into there out of an act of rage, trying to murder him, or to let him find the light so he could leave the island like the scientists said, but maybe he threw him into the cave as the ultimate FU to him, saying, since you are now one with the light you will never leave this island ever!
2) Across the Sea gives us the most logical place for a new lost series. The story of or before Mother, aka the true island story. Since the Island is underwater now and they are leading us to the conclusion/death of so many characters, if a spinoff did happen, the odds of it containing the same actors/characters from the original LOST are astronomical, it would have to be a whole new set of people and stories.