The best podcasts in my experience are:
1. Those that are tightly written and edited. That is, there is a script (which can then, of course, be posted).
2. Are discussions (lectures, interviews, conversations) about a text (book, article, concept, etc.) which itself can then be referenced for more detail.
3. Are narrations of short stories.
Examples of these would include:
- Numerous history podcasts: The History of Philosophy (Without Any Gaps) by Peter Adamson, History of Rome, History of Byzantium, History of China.
- The New Books Network, a series of author interviews on recently-published academic books. Here you're listening to the author and an (almost always academic) interviewer discussing the topic, effectively as an advertisement for the book. It's a great way to be introduced to deeper material.
- A few deeper / prepared podcasts. WNYC has numerous professionally-scripted podcasts, as do other NPR / public radio / government media affiliates in the US, Canada (Ideas), BBC (Tim Harford, various), and elsewhere. These blur the line between traditional podcast and commercial broadcast, but are quite intelligent and informative.
- Stories or nonfiction narrative. "Selected Shorts", "Soundprints", "This American Life", "Reveal", and others come to mind. Here the idea is to simply be entertained or caught up in the narrative.
- Various interview programmes. I'm fond of Terry Gross's "Fresh Air", the Santa Fe Institute's "Complexity" podcast, and others.
None of these is the proverbial dude/chick (and optionally friends) blabbing incoherently into a mic. All are scripted, most have either transcripts, extensive show notes and references, or both (the fiction / narratives being the exception). For the record, the unorganised / low-content flavour of podcast is one that drives me nuts as well. Sturgeon's Law applies. Seek the non-cruddy end of the spectrum.
For times when I'm read out, or otherwise engaged (kitchen, chores, driving), or want to zone out, these are worth listening to.
For conveying infotech content, I'd generally agree that podcasts aren't the best medium. I also generally stray away from anything that's strongly focussed on news, current events, or current topics, and the list of academic, historical, and philosophical programmes above have been quite the useful informative distraction from the moment for me, for the past several years.