My thoughts have been a mix of everyone else's -- truthfully, his removal from the political talkosphere feels like a great boon. But he had a wife, and four kids, and if he was just 43 those kids have got to be both young enough to be totally, nakedly devastated and old enough to really understand the magnitude of their loss (and I can't imagine what the combined weight of widowhood and single parenting four children is going to do to his wife). I'm glad his voice is gone from the public sphere, but I wish like anything it was gone because he'd suddenly retired, or had a conversion experience, or anything else that would let his family keep their beloved husband and dad.
eta: Even before I'd read about his family and realized what a huge howling loss his death must be to them, I was still kind of surprised by how not-happy I was to hear that he'd died. For someone just my age to go to bed, apparently healthy, one night, and probably noodle around with crosswords or sudoku or a chapter of whatever they were reading, and set it down and set the alarm and sigh and roll over and then just never wake up again... no matter who the person was, that just feels so viscerally, wretchedly unfair.