This is what I wrote before the episode aired:

This is the make it or break it (use it or lose it?) moment for the show. It’s frustrating to me that I am so firmly in the show’s pocket that even if every single remaining episode is really bad. At the same time, I’m really hoping that this is the episode that hooks me for the rest of the season.

Now? Hmm.

It’s true that almost nothing happened in this episode. On the other hand, I mostly enjoyed this episode, and it actually (for the first time this season) delivered on the writer’s promise that the final season would recall the tone of the first. When I rewatched the series in anticipation of the season five premiere, I remember being surprised at how little happened, in terms of wider mythology, in the first two seasons. In many ways, all of seasons one and two are very slow set ups for their finales.
Now, I don’t think this excuses the writers from fan reaction (or at least fans like me) to season 6. The head writers like to talk about a dichotomy between character-based story and mythology-based story. They claim that fans clamoring for more “stuff” to happen are showing a bias towards mythology, and that they want to keep their show grounded in character motivations and interactions. I think what is missing from this discussion is that in the early seasons, even in character based scenes like the flashbacks, what kept viewers interested in the show was the prospect of discovery. In the first two (not so much three) seasons, finding out something about a character’s backstory was exciting, and that had both to do with character elements (for example, finding out the hidden motivations behind a characters on-island actions [I think this was best done with Sawyer’s flashbacks]) and mythology (one of the greatest thing about the early seasons was the way that they tied the characters together through common elements of mythology, most notably the Numbers). I don’t think that the line between character and mythology has ever been clear on this show, and to ignore one for the other is going to throw off the viewers.
Another big structural problem is the alternate timeline scenes. It’s touching to see some storylines that we know from flashbacks get positive resolutions (Locke in a stable relationship, a seemingly happy Ben and Roger, Jack less of a mess), but there is no weight involved in these timelines. I’m not sure why I should care. Is this the timeline after the events of the Season 6 finale? Is this timeline going to go away? In the official podcast, the writers mentioned that they don’t like fans thinking about the alternate timeline as an alternate timeline, I guess they want people to view them equally. But it’s not really their right to say that their fans are viewing the show wrong. Some kind of explanation or clue as to why this timeline matters would go a long way towards making those scenes feel important.
What did I think of the episode? This episode  didn’t have the strong hook that I was looking for; no “Oh shit” moment. On the other hand, I thought it was a good episode, and many of the touches, especially the slow motion/dramatic music ending*, brought back the dramatic tone of season one with genuine nostalgia.
Other thoughts:

• I like the LOST writer’s use of wit: a great example was the segue from Island-timeline to alternate-timeline linked by Ben’s lecture on the significance of the island of Elba. Another was the great exchange between Richard and Jack: “Where have you been?” “You wouldn’t believe me if I told you.” “Try me.” “Not yet.”
• Some bloggers, I’m thinking specifically of Alan Sepinwall, posit that the resolved tensions in the alternate timeline are a reflection of the choices that the characters make in the battle between Jacob and Esau (not-Locke). This would explain why Jack, Locke and Ben seemed to have resolved their daddy issues, while Sayid’s life is falling apart. It’s an interesting theory, and also underscores how the themes of daddy issues and childbirth weirdly pervade this show. Are there any character arcs that have nothing to do with parental conflict or pregnancy?
• The interactions between Alex and Ben and their European History club inappropriately reminded me of Rachel and Mr. Schu of Glee. I kept waiting for them to either break out in song or make out.
• I also thought it was touching that he was kind of able to atone for betraying her on the island.
• According to Lostpedia, the six remaining candidates are: Locke, Hurley, Sawyer, Sayid, Jack, and Sun or Jin.
• Some characters appeared just to remind us that they exist: Sun, who along with Jin is underused to a degree that the show should be ashamed of, got some lines this week; Lapidus, who I like but at the same time never seemed as important to the mythology of the island as any of the other Widmore mercenaries; Miles, who showcases two of his talents: using blunt language to poke right at the sore spots of a character, and also to deliver memorable lines even when he only has a handful.
• The plotline with Ben and Arzst was weird. I couldn’t tell if Arzst only speaks in movie cliches or if it was just bad writing.
• Alpert’s line about how Jacob’s touch was a curse, along with his desire to die, recalls Michael in “Meet Kevin Johnson.”
• A lot of character reversals: Jack convincing Alpert that he has a purpose with his faith, Ilana forgiving Ben for killing Jacob, alternate timeline Ben making a decision that’s not for his benefit.

*Accompanied by Michael Giacchino’s (who just won an Oscar for the score for “UP”) terrible score. Seriously, the music for The Incredibles is one of my favorite movie scores ever, but his LOST music is godawful.