Our Calculus teacher is out on maternity leave for the next few weeks so she hasn't actually tried it out with live students yet. I only rarely visit the gradebook to see how quizzes with essay questions are shown there. In the quiz interface, students are told that it still needs to be graded and no score is shown however. Not sure really what the story is there.
What about tweaking your review options so that they can see more detail about the multiple choice questions they took even though they can't get a full score until the essay question is graded.