Regarding Jin, I coulda sworn in season one he tipped it off that he could speak English through one of his backstories. Gotta pull out my DVD's for season 1.
One thing that kind of bugs me is the loose attachment of the backstories to the current stories now though. Locke's "leap of faith" story with the leap of faith pressing the button to me seemed like just an excuse to show more of his story. While in the past, the backstories were kind of like what the character was thinking about at the particular time, I didn't think the whole Locke story in this episode had quite a direct relationship to what was probably going on in his mind in quarantine room.
They're kicking ass in the ratings. Too bad that the cast members are getting discouraged about the relative lack of attention they're getting though. Guess it's because they're looked at as sweaty and stinky unlike the sexual image of the housewives...
http://imdb.com/news/wenn/2005-10-06/#3