I prefer text. Audio and video are great and it's fun to actually see and hear the people who are making the game happen, but in many cases I'll only have the time, interest and patience to watch/listen to a small portion of what's released, and it's very useful to be able to skim a text document to get right to the portions of an interview that most interest me. So give us transcripts wherever possible, pretty please!
I check WoW insider most frequently, and look at MMO champ once or twice a week. And I love reading the Blues' thoughts on twitter, particularly Ghostcrawler.
Can't really think of a standout for best interviews, and I certainly can't think of any I didn't think were worth the time I spent on them. I think you guys do a good job of picking people who will ask the right questions and do it in an engaging way.
I love the panel format and think it gives an opportunity for a single discussion to cover a lot of ground. If we were to get only one developer interview I'd want it to be that format. But luckily we aren't in that position, and I think a one-on-one gives the opportunity for a lot more depth on topics like class balance and encounter design.