A few thoughts, to be expanded upon as time permits. Spoilers.
I was nervous about the premiere beforehand and very enthusiastic afterward. I don't know why I didn't see the alternate timelines coming-- it's very Abrams, and we've always had parallel narrative tracks on the show. But I didn't, and it perfectly solves the problem I was most nervous about--that neither post-Jughead option could be satisfying.
I was really, really right to think that this season theology would take center stage, crowding out political theory, philosophy of time, free will and causality, and so on. (For that reason, I didn't reprise my "Lost and political theory" talk last night; I have little to say about the theology.) And that's OK. But still...
There were a lot of Jesuses-- Jessuses? Jesi?-- running around last night.
-Sayid, who came out of the baptismal pool in a groan-inducingly-Godspell-like crucification pose, telegraphing the final moment of the episode (which was further telegraphed by Miles' listening to Sayid a few minutes later)
-Christian (ahem) Shepherd (ahem), whose body went missing sometime before they
-Jack Shepherd, who hasn't really done much Christ-standing-in to justify his name up until now, but now seems set to make the crippled walk
-and Jacob, already an established healer, whose power raises Sayid from the dead, who is sacrificed by someone who knew not what he did, who appears to one follower after his death, and whose body (again) disappears.
This isn't really a complaint, but it's a new worry, since all of these seem to be in for long-term Jesussy plotlines. Part of what was so interesting about the political theory and time/ causality references was that different characters and different viewpoints and different symbols were in play for each. I hope they figure out a way to do something similar for this season's theology.