The other's still have control of desmond's sailboat, if they still know the compas bearing on how to get off the island they still can. i mean it'd still be a one way trip, but they can still get off.

Oh schnaps! You bring up an excellent point! There is still a chance off the Island. I will bring up that idea and credit you by linking to this post.

http://thefuselage.com/Threaded/showthread.php?t=73260

Any method of sailing from the island would probably work, if it was done on the right heading. This is based on what Ben told Michael at the end of season 2. There's no reason someone couldn't build another raft and leave if they have the right bearing.

The Others have more than just Desmond's boat:

http://gallery.lost-media.com/displayimage-1256-910.html (http://gallery.lost-media.com/displayimage-1256-910.html)

The boat that the ride on from Alcatraz BACK to the Losties island is different from Desmond's. So if the submarine is the only way to get off the island, as it seems to be by what Ben said last night... hmm....

I was wondering about that last night. So what makes a submarine different from a boat? Sonar? But wasn't that disabled when the sky turned purple?

Already being discussed here:
http://www.thefuselage.com/Threaded/showthread.php?t=73282