I caught three on the whodunnit one: the roses to lilies, the different clock and the different dead guy (and I only noticed that because I noticed the replacement guy's vest and thought, "That's a cool vest...wait...").

I love this kind of stuff. I wonder if being right- or left-brained has anything to do with who notices changes and who doesn't? I know it changes how we perceive things (right-brainers tend to observe things as they are, and left-brainers see things as their brain thinks they should look).