I love -p, but it still falls short of darcs interactive commit (which it is definitely inspired by).

darcs interactive commit allows you:

- to add files in the same process (in two steps: intent-to-add and then the file itself) - revert of hunks, file additions, etc.

Yes, you can do both through separate steps (git checkout -p for example), but darcs interactive was a quick way of incrementally building full patches in one workflow.