Thoughts:Notice how similar Jack's conversation with Juliette was to Ben's conversation with Jack/Locke last season? I'm sure there was an intentional mirror.
Notice Ben mention "SUB".
If you look at Rousseau's map(s) (cut/paste the whole URL) (http://lost.cubit.net/forum/index.php?action=gallery;sa=view;id=58) there are islands and even one map has a profile of several satellite islands.
If you look at the blast door map (cut/paste the whole URL) (http://lost.cubit.net/forum/index.php?action=gallery;sa=view;id=97) (which is sadly gone, now... maybe), you will read a blurb about "subterranean conduit?". Bet this is how the Others get around so fast.
Juliette being a doctor reinforces my belief that the Others are the remnants of the Dharma research scientists. I would put money that Ben was lead scientist.