Lost has really refined the whole last-shot-surprise-reveal thing this season, so much so that its predictability seems to be turning a few people off. One thing that I don't see getting a lot of attention, though, is how well they're working the thriller approach that they seem to be riding.
Consider the very different ways that irony is deployed in the last two episodes. In 4x03, Sayid tells Locke that the day he trust Ben is the day that he sells his soul; in the flash-forward, he's working for Ben and trusting him with his life. A week later, 4x04 gives us a flash-forward where we're told Kate has a son and an island-time narrative where Kate assures Sawyer that she isn't pregnant with his baby. 4x03 has primed us to believe that this exchange means it must be Sawyer's baby, (and Kate's awkward exchanges with Jack in the flash-forward further suggest this) but the producers play with that expectation in order to swerve us again at the end. The baby's not Sawyer's, it's not even Kate's - it's Aaron, Claire's son. (And then, of course, you remember that the psychic told Claire that she had to raise Aaron, which makes things that much more ominous...)
So maybe Lost has been a bit one-note thus far. But as long as they manage to keep playing-off what they've done without obviously repeating their tricks, it still works ridiculously well.