The Shat talks about the decision to kill Spock and the fan reaction a great deal in his book Star Trek Movie Memories, which I highly recommend for the entertainment value. He's a hilarious dude, and a glimpse into his brain is pretty awesome. ALSO, the saga of Making Star Trek 5 (aka Shat's On Crack And Wants You To Be Too) is possibly EVEN FUNNIER than the movie itself, which is saying something. (One of the few times I've literally fallen off the couch laughing, dude. It helps having read the book first.)