I'm glad I stuck around to see the ending. As with so many movies, the Christ theme showed up. This one, though, took it a step further than the frequently-seen lead-character-sacrifices-himself-for-others plotline.
(NOTE: If you haven't seen the movie yet, you may want to skip the rest of this post. Go rent the movie, watch it, and then come back and read. It's OK, I'll wait.)
Smith plays Lt. Col. Robert Neville, a military research scientist who spends his days searching for uninfected humans and attempting to isolate the antibody in his own blood that makes him immune to the virus, so that he can create a cure that will return the zombies to their human state.
After experiencing failure after failure as his lab rats die or remain unaffected by various formulations, Neville sees a glimmer of hope in one rat whose behavior and appearance have returned to normal, so he traps one of the zombies for a "human clinical trial."
The antitoxin looks like another failure up until the end. By this point, two fellow survivors (Anna and Ethan) have found Neville, but they have carelessly left a trail of blood, and the monsters have tracked them down and invaded the house.
As the three lock themselves in Neville's lab, he notices the clinical-trial zombie has recovered. He knows he is trapped, but as the zombies begin to break through the lab's plexiglass wall, Neville sends Anna and Ethan to hide in the lab's safe.
Neville draws a vial of the now-recovered zombie's blood. He hands it to Anna with instructions to stay hidden in the safe until morning, then reaches into a drawer for a grenade.
Just before he pulls the pin and rushes through the lab wall into the zombie onslaught, Neville leaves Anna with these words:
"The cure is in the blood."
So we have a man, immune to the disease that has wreaked havoc on the world, giving his life to save the endangered... and his blood to save the fallen.
Sound like anyone else?