I won't go into this too much, so as not to spoil it for anyone, but last night's episode of Lost is a prime example of everything I love about this show. The end is nigh, and we've been begging for answers, and last night we discovered the origins of the never-aging Richard Alpert (a fantastic, Emmy-worthy performance by Nestor Carbonell). We also discovered what the Island really is (hint: its a four-letter word), and more about the long-running feud between Jacob and the Man in Black.
Richard, in his past life
Which I must comment on: I've read a lot of fan comments on message boards about how the show is devolving into being just about those two characters, neither of whom we'd ever seen really before this year. I completely disagree. They are driving narrative forces, yes, but their conflict is merely an arena for the main characters that we have grown to know and love over the past six years. The show is still focused on the castaways, and now its how they fall in this power-struggle between "good" and "evil." I'm glad to see that the moral ambiguity of the show remains, and that the point is still (hopefully) about these characters discovering their true selves.
If you missed "Ab Aeterno," or just want to see what I'm raving about, watch the episode here: http://www.hulu.com/watch/136820/lost-ab-aeterno.