My impressions:
On Juliet: Juliet said to Jack "I'm already on my own" I took this to meaning that she is playing both sides to see who will give her the best chance to get off the island.
On the Others: The episode was a very good glimpse in the dynamics of the Others.
On the pregnancies and Claire: Well, fist let's remember that Ben once said he was born on the island. So, either something happened so that women cannot conceive anymore or they really can and they are simply using them as guinea pigs for something other purpose. Claire's life was never in danger and she would of given birth regardless. In this, either Juliet is lying or was lied to. But I believe the former because of well the implant they activated but Juliet told Ben after being on the island for 6 months that the problem is at conception. So, because Claire had conceived off the island, she would of been safe. But that may not be so for Sun. If Sun conceived in the island, then her life is in danger. But if she was pregnant before coming to the island by either Jin or her now dead lover, then she should be OK.
On cancer: Ben lied to Juliet and her sister's cancer never did come back. They could of easily falsified the records he showed her. Then, how could he have "cured" her cancer without bringing her to the island? And how do you explain his own cancer? I believe the island chooses who it "cures".
On the Black Smoke Monster: There are 2 people who think they understand the island and claim to have seen into its very heart: Locke and Eko. They are also the only 2 to have faced the monster. It later came back and killed Eko. I don't think it killed him because he was a "bad man". I think that's a bit of a red herring because there are alot of other "bad people" on the island (Sayid, Kate, Sawyer, Niki, Paulo, Sun, Locke and to a lesser extent Desmond and Charlie) who have not been killed by the monster. I think that the difference is that Eko actually learned the island's secret while Locke hasn't or only thinks he has. That's why Eko was killed; to prtect the island's secret.
Just some thoughts.