Given that I have listened to no more than three podcasts and have found no more than one useful, I would have to agree with Werner Vogels' desire for more navigational structure.
I believe my main problem with the format is you are supposed to use it linearly. I love to read articles, papers, books, etc., but I am often a non-linear reader. I will scan back and forth for interesting pieces. The fact that you cannot build a hierarchical model of a podcast for selective drill down is pretty annoying to me...I would probably pay more attention to podcasts if they were written down. 8^(
It is not that I want everything written down... I believe more structure would be absolutely helpful.