I like having a "successors" column to complement the "predecessors" column - I use this to trace forward to find tasks that are affected if I make a change. However, the successors() function returns not only immediate successors, but every task that is a child of those successors. While this may be technically a true result, it is a different result than I want - just as "predecessors" contains direct predecessors, I only want to know the direct successors.
Suggestion, then, is to add a parameter to successors() to instruct it to return only direct successors.