Okay, so I know a lot of people enjoy podcasts. But personally I really don't care for them. First up there is an annoying tendency for podcasters to not tell you how long the podcast is. How am I supposed to know whether I have time to listen to the whole thing? Can I listen through it while I'm getting ready for work in the morning or is it a huge 3-4 four hour monstrosity? Annoying. Also, a lot of podcasts contain a lot of stupid "banter", the vast majority of which is not particularly interesting or amusing. They'll toss out an inside joke reference and all have a good, long laugh about it together. Super. Whatever.
Another thing is that I read very, very quickly. I can scan a huge written post and quickly tell whether I want to take the time to really read the whole thing. Or I can scan and just slow down for sections which grab my interest. With a podcast you have to listen to pretty much the whole thing (well, okay you can skip around but it's not as efficient as skimming text) to find out whether you've just wasted a bunch of time.
My wife tells me from her background in early education that people learn in one of three ways: visually, aurally, or manipulatively. So I suppose that if you're an aurally oriented learner then podcasts, which are a purely audio medium, would be optimum for you. I, however, am primarily visually oriented and secondarily manipulative/manual. Thus I find that I cannot sit for long periods listening to disembodied voices drone on about whatever.