I’m going to go ahead and be “that guy” and echo something from the other comments:
I think that we need to make sure that WorkFlowy does not become like other task managers that have too many options. I especially don’t want to encourage myself and others to fall prey to putting dates on things that don’t have dates. I’m thinking here of the GTD dictum that the only things that belong on a calendar are things that die if they’re not done on that day.
Another thing I’m afraid of with reminders and hiding items until certain dates is that it may discourage regular reviews of your lists. I’m already terrible at this, but I want to get better. Having automation hiding and showing things is only going to serve to make me worse at reviewing as a habit.
That’s my two cents, though. Love the app, use it religiously.