The Complete/Incomplete grading is an all or nothing approach. If you are using a rubric in conjunction, the thought is that perhaps there is a threshold and when students meet it then they get credit for the assignment. If you prefer to grade specific points from the rubric, then perhaps the Complete/Incomplete approach is not what you are looking for.
I've found it useful for low-stakes assessments, such as reflection papers and benchmark deliverables to keep students on task. I might have pass/fail checkpoints leading up to a final capstone deliverable, for example.
