I was pretty pissed (but not terribly surprised) when his nose started bleeding and it became obvious that he was going to die. I believe I used a few colorful metaphors directed at the producers of the show.
I agree that it's a gutsy move, but it's a gutsy move that lacks any real compelling reason except to be a bummer for the audience. On a show like this, having a happy ending after all the misery these people have been through would probably have been more surprising.
It's like '24.' Ending that show on a down-note with Jack dying (as one of the producers have suggested before) wouldn't shock me at all, because after all the depressing stuff that's happened to the man over the years it's what you'd expect. If you want to shock the hell out of me, have Jack marry Agent Red and then have them ride off into the sunset with Kim on some ponies singing 'I'm Walking on Sunshine' or something.