(1) Difficult to quickly, skeptically, impatiently (the universal trinity of user behavior) distinguish audio vs. video files. LESSON: Even though you may display the full URL of a file, in common usage (.wav, .mov, .mp3, etc.), audio podcasts still need to appear in an isolated clump for easy inspection and expedited downloading, they need to be set apart, with distinct and uncleverly labeled Audio and Video tabs in your home directory page, contents listings, or portal index.
(2) Podcast mp3, when downloaded and an Open attempt is made via your favorite multi media player/archiver/disk burner, an error message pops up: it's PHP file. LESSON: Keep your mp3 links active, or delete them. Nobody likes linkrot dead files.
(3) Long rambling interviews with marginally non-self promoting clueless pundit wankers. LESSON: Better to podcast yourself and your own ideas, than attempt to promote others in a mutually opportunistic and mercenary manner.