I just finished the novel and I have to say, Orwell's prediction of the future is definitely one of the most chilling I have ever encountered.  In the end, Winston is broken down completely, and his ultimate betrayal of Julia seems like it was inevitable and unavoidable.  The whole novel explores the possibility of what could have happened had the Nazis or the Soviet Union taken over.  It's especially chilling when we realize that Orwell's world could have come close to being a reality, and it's even more chilling to think about the fact that there are similarities between Oceania and our world today.
The book overall captured me from start to finish, and when I read the last four words, "He loved Big Brother", I think I realized for the first time how much power the Party actually has over people (298).  Winston tries to resist, but in the end he can't, and his entire way of thinking is turned around.  The scariest part about it, though, is that the way he is tortured and made to think seems completely feasible.