Works very well. The GUI's a bit confusing—I wanted to save audio, so I selected that in the list, but nothing seemed to happen. Then I clicked the Save button, and again, nothing happened (no progress notice, etc.)—but then a file window appeared about 20 seconds later and I was able to save the MP4. I've seen other extensions that could save audio in the more compact MP3 format, so that would be a good idea here too.