Thanks for the advice. So whenever it is PCM the video suffers a bit? Normally it just records far less video and audio (an hour, as opposed to 2 hours when no PCM), so I assumed that the video rate was constant. Still, I'll keep that in mind.
If anyone's interested, here's an audio capture of the King Kong Criterion Commentary in WAV format. It's very listenable, and the first commentary ever made. I captured this in AC3 though because I didn't think that such an old Criterion would have audio worth capturing in PCM. However, I'll probably try capturing it that way another day. Here's the download link: