Best Episode EVAR. We learned so much. Here's one thing I found wierd about it though. The conciousness switching from one point in time to another is understandable. It can only be in one place at one time and that's how it was all the way up until the phone call with Penny. But then we see Desmond get the number, switch to 2004, make the phone call, and as he makes the phone call we see 1996 Desmond walking away from Penny's house in slow motion with a smile on his face as if he knew that it worked. I think that was a mistake on their behalf... just pointing it out.
Also, the nose bleeding and convulsing thing. If desmond dies in 2004 will he be alive in 1996 still?