I agree with everything Kirobaito said. Except the Oxy Contin thing; Jack has just gone insane or something. You'd have to be on <i>a lot</i> more Oxy Contin than Jack was to think your dead father was back alive.

Also, Michael Emerson is a great actor, I think. Although I did not like him in Saw, he is expertly creepy and strange in Lost.

In an interview Michael Emerson talked about how his character works as a villian on the show since a lot of American viewers find his character evil because an intelligent, sophisticated and educated man is viewed as creepy and wierd in the US(i.e. Hannibal Lecter), whereas the character would not work as a villian in other parts of the world as well because the type of character he has is more accepted and "normal".
I think Ben works outside of America as a villain, as well. He's evidently crazy, ruthless, remorseless, and knows how to smurf with people's minds. It's wonderful!