FWIW, I think this is important, but I'd like to pick. I have many tasks that I know can not be worked on until a certain day, but might not get worked on even then, so I would want those in "Next Actions", but I have others that can't be worked on until a date, then need doing that day. If I understand correctly, GTD identifies these differently, as one would go on a calendar, and the other would go in the tickle file. Perhaps it could even be that "scheduled" tasks act as you suggest, and "waiting" tasks can have an optional date field that would work like a tickler.