This is the official Wizards of the Coast podcast for D&D, so its now based on 4e. I've had ambivalent feelings about another edition of D&D being released which I've previously discussed so I'll just concentrate on the podcast itself.
The regular presenters are Mike Mearls and Dave Noonan, both from WotC D&D division. Mike Mearls is well known as a scenario designer for many different companies including Necromancer Games and Goodman Games. Dave Noonan is another member of the design team whose work I don't know so well. There is a good interplay between the presenters with Mike Mearls tending to deal with answering most of the questions in the mailbag episodes.
The content is mainly discussion of 4e D&D which is hardly surprising, but there have been episodes talking to Wizard's other designers from products like Star Wars SAGA edition. The discussions with other designers are to highlight how 4e D&D doesn't stand in isolation from the development of games like Star Wars SAGA edition or earlier versions of D&D. There have been a number of episodes solely focused on answering questions from listeners and the latest podcasts feature a game being played with the crew from the Penny Arcade webcomic.
The sound quality is excellent, but given that WotC has a major corporate parent in Hasbro I'd expect them to invest the time and resources to make this work well. It downloads easily from iTunes store and the WotC site.
If you are playing 4e D&D I'd rank this as pretty essential, if you are interested and want to find out more then it would definitely be a useful information source though with a clear bias towards 4e. Obviously if you have no intention of