The episode starts off in the right direction, with the revelation that at least some of the Oceanic Six have survived the return to the island. The initial headcount is a bit surprising: Hurley and Kate were not among those standing in the room when Mrs. Hawking explained the transient nature of the island and how they all might return. By the end of the episode, that initial mystery is still left unsolved, which is sure to be a point of contention.
It wouldn't be the only one. For some reason, this episode felt a bit disconnected from the flow of the season thus far. Perhaps it has something to do with the decision to air this episode a little bit out of order; the next episode was originally intended to air first. Time will only tell if it would have made a compelling difference, but this episode just didn't have the same kinetic spark.
It might have been the intense focus on Jack. No episode this season has been as focused on a single character. It's something of a return to more familiar waters, and that will hold its comforts, but is Jack really the right character to give this kind of focus? His journey in this episode is not particularly interesting, and seems designed to facilitate a distinct lack of information regarding the decisions and experiences of the rest of the Oceanic Six gang during those final 36 hours.
Even the mythological explanations seemed a bit mundane. The need to have all the Oceanic Six on the plane, ready to return to the island, seemed like it had a very specific context relative to the secrets of the island. That's still true, but it's less well-defined and a bit too vague as presented. The trick, it seems, is to arrive at the time-specific location of the island (or close enough proximity) under conditions as similar to the original arrival. It is the parallelism rule that demanded as many of the Oceanic Six as possible; not something necessarily specific to those individuals.
For whatever reason, this amounts to using Locke as a "proxy" for Jack's father. That doesn't preclude the notion that Jacob will take possession of Locke's form once the body returns, but it is a lot less interesting a reason to bring Locke than one might have hoped. And while Jack certainly struggles with his faith in the plan and the island (as one would expect Jack to do), the questions surrounding other characters seem a lot more interesting in comparison.
Kate's decision is possibly the most enigmatic and compelling, because it pertains to Aaron. Kate was warned by some spectral version of Claire to ensure that Aaron never went back to the island, and she seems to have kept that promise. But why wouldn't she want Jack to know where Aaron was taken, even after they returned to the island? Despite sleeping with Jack, her attitude on the day of the flight is remote, to say the least. It's typical Kate, which just begs the question: what is she running from this time? (And does it have anything to do with what Sawyer asked her to do on the helicopter in "There's No Place Like Home"?)
In Ben's case, it seems that his comments about being banished from the island were premature. Maybe he never imagined that he could find the island once he moved it. In the end, it's not particularly important; Jacob will sort things out in the end, anyway. But his last minute business had some obvious and troubling overtones. He called Jack from the docks, which is exactly the kind of place that Desmond's yacht would have been. That implies that he might have made his move on Penny Widmore, knowing that he might never have another chance. Nothing is certain, but things aren't looking good for Mr. Hume's family right now.
The other characters were either sidelined or came out of the blue. Sun's conversion doesn't address the rather important matter of her daughter, which is disconcerting. Sayid's return mirrors Kate's original circumstance on Oceanic 815, and he seemed surprised (and then resigned) when he saw the others. The new passenger, Caesar, seems too well-positioned (much like the new marshal, Ilana) to be a simple extra, but his purpose is completely unknown at the moment.
Only Hurley's presence seems to point to some island-based demand that the Oceanic Six return to the island. This could easily tie into Hurley's visitation by "Charlie" in "The Beginning of the End". There's evidence that this was really Jacob, communicating the need for Hurley and the rest to return to the island for the same reasons they are now. Given that Hurley is carrying a guitar (presumably in Charlie's stead), it's reasonable to assume that "Charlie" paid Hurley another visit.
By showing that the Oceanic Six (or at least some of them) made it back to the island, much of the tension of the situation was strangely undercut. Then again, there was never much doubt that they would return to the island anyway, so perhaps it didn't make much of a difference. What is interesting, however, is the revelation that Flight 316 crossed over the island during a time flash, apparently aligning at least some of the returnees with the rest of the tribe.
And that tribe appears to be, as predicted, in the 1970s Dharma Initiative era. This aligns with the season premiere, and Jin's apparent role in security suggests that some or all of the tribe have infiltrated Dharma. It may also mean that bringing back the Oceanic Six may not have meant the automatic end to the time flashes. If so, the body count may continue to rise.