Rob,
I'm continuing my quest to listen to all the podcasts! I just finished listening to episodes 8-12 and have a couple of comments:
Since you are creating a valuable archive of shows, it is important to make them as useful as possible as archives. A couple of things came to mind as I listened to the shows and downloaded them:
1. When refering back to older shows, it would be really good if you could list the actual episode that covers the topic being discussed. It was either episode 11 or 12 when you said something to the effect of "back in the early episodes, but not #1 or #2". While you do have some very dedicated listeners to this show, many educational studies (wish I had references) have shown that it is unlikely a learner would listen to several shows just to find the one they are after. If you don't want to delay the recording of the show as you look down the list of almost 80 shows, you could say I will include a listing of the exact episode in the show notes or something like that.
2. Try to make your show descriptions more concise and specific, so that when users are browsing through your shows it is easier to choose ones to download.
For example: In Itunes you have the description
"Question and Answer Show #2".
It would probably be more helpful to people browsing the shows to see a title like:
"Q&A Show #2: Substrate, Color Lighting and Water Movement"
These two suggestions could help your archive of shows be more useful.
Just trying to offer some constructive ideas

The audio quality took another jump with Episode 12, it is almost like I'm listening to Rob and his podcasts growing up
Brian