Chills, I tell you. Just the significance of what that one word "Croatoan" means -- I have chills even as I type this! Very, very powerful episode, from the first slo-mo vision to the last moment there. Excellent set-up and then Dean being so damn cold and ready to kill. And ready to die. :-(
GAH! Just when you think you've seen the maximum strength Winchester angst, they raise the bar.
Can I also say how much I liked the Master Sergeant character? Sorry to see him go. Think he would have made a better Gordon, actually. One of the few times I laughed all episode was when he gets into the Impala, gun drawn, while Dean is covering him with his gun and Dean says, "Well, this is going to be a relaxing drive." (Or words to that effect.)
I'd skimmed my flist and saw that it was a cliffhanger so there was less, "OMG, no!" from me, probably. I actually thought they might leave it with Sam infected and at Dean's throat or something, so as cliffhangers to, not that traumatic. And as far as the virus disappearing from the blood samples ... until the possessed guy (Dwayne?) said Sam was immune, it seemed like maybe Sam wasn't after all. Not that there's any coming back from being possessed, most of the time. And also, if anyone ever is alone with me a car in the middle of somewhere, and says they want to make a call and doesn't pull out a phone? I'm throwing them out of the car!
Can I say again ... AUGH! Dean! *clutches heart, wipes away tears*
Also, zelda_zee has written a lovely, angsty ficlet set after this episode (her first SPN fic!) HERE 'tis.