Of all the podcasts I have tried, I only listen to two regularly. One is the Mars Hill church podcast for the music (enough with the preaching and interviews allready!), and the other is The bored-again christian, a kind of radio program show (mostly music), both available in iTunes.
To be honest I don't like podcasts very much. I've used many podcasts in the past, but stoped hearing most of them shortly after. News podcasts is a no-no for me, I prefer reading news. The same with interviews.
So, in my opinion, what are podcasts good for? For everything that text and images is not enough. And what's that? Music, of course. There is no substitute for a podcast when the deal is music. And if somenone has the kind of music you like, like Mars Hill, and they offer it for free in a podcast, that's great.
On the other hand, podcast are excelent for blind people. And that's why I'm thinking about podcasting some content in this blog. We shouldn't exclude people with disabilities. And also, there are some people that don't like reading text in the computer, and want to take advantage of the time they spend in traffic/transports. For those,podcasts are great. I prefer reading a book and listening to music (yes, at the same time), but someone who is driving can't really read a book, can he? But not me, I use public transports.
And what about videocasts? Well, a similar rule applies: Videocasts are good for anything for what text and sound is not enough. In that sense, a videocast of someone telling you some news, or with a interview, is the biggest waste of time. Videocasts are cool for anything that requires some movement. Like cooking. Or music videoclips. Crazy stuff. But not for news.