I would just like to put in my vote for a move from an audio-only podcast (I really do wish you'd stop calling it a "radio show") to a video-based one. Nowadays, it's so easy to set up Skype sessions with interviewees who are outside the production studio. And I think it would add a lot more interest to the show: we could actually see what a pipemaker's product looks like, we could see a collector's collection, we could glimpse what a tobacco blender's workspace looks like. Of course, it would be wonderful to actually see several folks in the studio together, talking pipes, but I realize that simply might not be logistically possible.
I'd also suggest that the ads shift away from being canned, repeated radio-like commercials. Why not have the host just read an ad, once from each underwriter, during the course of the show? I can't tell you how tired I get of hearing the same ads multiple times during what is already a fairly brief podcast. (And if we listen every week, the repetition gets extremely annoying.) And the fact that they play like radio commercials just feels odd for an Internet-delivered podcast in 2013.
My .02 anyway...