Audio commentary question

I mentioned a couple of weeks ago that I'm experimenting with providing audio commentary on students' drafts this quarter. For their first project, I responded with both extensive written commentary and fairly-extensive audio commentary. It took a lot of time, but I wanted students to experience both forms of response.

For their second project, I gave them this option: either written commentary alone, or audio with minimal written commentary. Out of two classes, only four students chose the first option. So I'm thinking they really like the audio.

One glitch, though: I was talking to a senior colleague about the whole audio thing, and she didn't seem to be too keen on it. Her main objection was what she called "a literacy issue"--she said that students should have to get used to reading/interpreting instructors' written comments on their writing.

Hmmm. Does this colleague just have a very limited, print-centric conception of literacy? Or is she just anti-technology? Or does she have a point?