I'm curious how "Copy files to iPhoto Library folder when adding to library" works if toggled while managing a single library. I prefer letting iPhoto managing its internal file/folder automatically (the pre-'06 behavior) but could see the new option being useful for additional content in externally organized folder (e.g miscellaneous images under ~/Pictures) that I've intentionally kept out of iPhoto until now. I do something like that with iTunes, which is more restrictive than iPhoto since it still only supports a single library.

Maybe it would simplify things to have multiple iPhoto libraries, some auto-managed and others not although that doesn't eliminate having to remember to set the copy preference appropriately. At least we've got that option now -- thanks for mentioning it.