I will use the following criteria for grading your podcast:
Is it interesting (subjective), the name of the episode, length of episode
The flow of the podcast, voice inflection, getting and sticking to the point, clear concise segments (when applicable).
Audio quality is clear and non distracting. Volume levels are not too low, but not distorted. The listener does not need to adjust or strain to hear the audio.
Proper ID3 tags, promotion of your site, contact info, etc.
Subscription buttons, show notes.
Consistent Delivery, Audience participation, great show notes.