But he said, several times, that it had nothing to do with his blood...this would make more sense to me (Jack coming back to life innumerable times) if it weren't related to his blood. The Blessing sucked an enormous quantity of blood out of him...enough to kill any mortal man...and since Rex had Jack's blood in him in Argentina, the blessing is reversed and *poof* Jack comes back. If it's not blood-related immortality, then Rex ought to be dead. So, that's a big inconsistency. Also (and I'm no M.D.), but if Rex's and Jack's blood aren't the same blood-type, doesn't Rex die anyway?
Other than those issues, still, I enjoyed the finale'...