What's a good podcast?

I recently emailed Thomas MacKentee of the Geneabloggers podcast about my idea for how to tell if you're listening to a good podcast.

You see, I had just been listening to the recent Geneabloggers podcast and just realised how to tell if I'm listening to a good podcast. Whenever I'm listening to a good podcast, such as Geneabloggers, Genealogy Gems or Genealogy Guys to mention a few, I always turn off my iPod for a few minutes when I cross a busy road. The traffic noise makes it harder to hear what is said on the podcast so I feel the need to switch off so I dont miss out on any of the good stuff. I suppose it's a good idea for safety reasons too:)

I wonder if there are other indicators that people have noticed in terms of how to tell if they're listening to a good podcast rather than a ho-hum one?