I use @Waiting and I review that folder from time to time (typically twice a week). If it is urgent, I will @Waiting it and put it in my task list with a due date.
If there are time zone issues, etc, then I will put it @Waiting in tasks, and then move that task to my calendar and explicitly make an appointment for when I should follow up as well. I still review the @Waiting task at regular intervals, so the appointment is sometimes left there (if I forget to remove it) even after the task is complete. Haven't yet found a good solution for that specifically, as I have to go look at the task sometimes, then I realize it's complete, and then remove the entry.
Would be better if I had a way of removing the entry as soon as the task was complete, but my referencing is one way (Appt -> Task, from Task I can search for appointment, but it's not contained in it)