E, where are you!?
WOW is all I can say! 
I'm here now!
I'll be truly impressed if 10-year old Ben IS dead, AND they can explain how! I mean, Sayid doesn't really miss the mark, y'know? Was the last shot of Sayid going away from Ben and not checking the body? If so, then it's very likely Ben was badly injured but not killed. I'll be ok if it is an injury, though it certainly takes away from the shock value ending.
I've never had my jaw drop to the floor... at least not anytime recently I can think of. What an ending!!
And if these theories (this is what starts the big war between Dharma and The Others, etc.), I'm dying to know how it ends up/begins that the Flight 815 (and Juliet, etc.) people will have no recollection of this.
What I really want to know is what that bloody smoke-monster thingy is.