I don't sit down and watch it, but my wife and daughter are addicted. I usually get a play by play from my wife.
We have every episode... seasons 1-3 on DVD, seasons 4 and 5 were downloaded each week, then burned off as AVI files onto DVDs.
Just before each new season starts, my wife and daughter do their own marathon and watch every episode just before the new season starts.
Oh, for what it's worth... Keifer Sutherland signed on for three more seasons. He said he may or may not be IN the show, but he will be producing it for sure (it all depends on the writers whether or not he stays).