I agree.

While not a direct replacement for lectures, I've been prototyping an audio media which does not have these same disadvantages, called push to talk. You can find the prototype here: http://thobbs.cz/push-to-talk/index.html

Click on the first track, and then use the arrow keys to move through the essay. Note that you can rewind, review, pause to think, just like with text. But it is speech.