This is a very tight episode, there is a lot going on but it has the feel of an episode where not a single shot is wasted. It's another episode where the action is spread over multiple locations; the flashback, the Others Barracks and the beach camp. The flashback bearing in mind the subject matter is the weakest part of the episode - plus it seems to mix up the Left Behind metaphor the episode is based around with Never Go Back. In order for this episode to work we need to see more of what Kate left behind. We get two good guest actors on show in the shape of Kim Dickens off of Deadwood and Elizabeth Broderick of Teenage Witchery fame - other shows may apply. They should have been given better material.
The stuff at the Barracks is brilliant, everything is from Kate's point of view - not from a camera Peep Show sense but it's certainly from her lens. Juliet is viewed as suspicious and Jack as some kind of end of level trophy that she has her aim on. There's a good scene with Locke early on which perfectly sums up his character, he's trying to be judgemental, aloof, looking for a moment where he gets to say goodbye and "ascend" but like Kate we don't care - we want to know where Jack is. We get a good set piece with Kate and Juliet handcuffed and encountering the smoke monster - we find out The Others don't know a lot about it and that the Pylon fence is designed to keep it out. The theme of this section is that The Others have gone and left behind everyone they (or Ben?) don't want - including Juliet.
The stuff at the camp with Sawyer and Hurley is lovely character stuff. Hurley manipulates Sawyer to be the leader they need in a series of comical set pieces and at this point we're getting the double act we didn't know we needed as the two characters bond.
It's a strong 8/10 from me and with a stronger flashback this could have been something special.