I have been working on a new question type that allows students to submit a single file and optionally an essay in response to a question. I think that this question type addresses MDL-8075 and the quiz question portion of MDL-8229, which both request the ability for students to attach files in questions.
The teacher can specify an file upload size limit and whether the essay field is displayed. The student can upload a single file and enter an essay. The student can't delete an uploaded file directly, but uploading another file replaces the previously uploaded file.
The attached question type works with recent versions of 1.9. Backups aren't working at this point, but will be updated when 1.9 is released.
Please let me know if you have any problems/requests for this question type. I'll post a follow-up in a second with a patch for 1.8.
Edited to add: screenshots of this question type.