I only want to see actionable items in my agenda, so if, for example, there is something to do at 4pm today then I don't want to see it till then, because I can't work on it anyway.
Currently I use org-agenda-skip-function for that with a custom function, but it would be a natural job for org-agenda-todo-ignore-scheduled. It has an option 'future' to ignore scheduled todos with future dates, but it's not useful for future times today. I recommend adding an option 'future-time' which does that.
