Great thoughtful post. And I have that same problem. Podfic IS more labor intensive than fanfic--there's more technology involved, more steps (for the podfic reader as well as the listener), more intermediaries (like an archive or a filesharing site)--it's harder work.

So I guess my thinking about it is that that one more step of going back and leaving a comment somewhere is part of the extra work, and I really try to do it.

As to what kind of feedback? I've gotten a little on my small podfic contributions, and it's a joy just to hear that I read a story well, or did it justice, or had a nice voice, or was clear in my pronunciation, or I made it easy for you to tell which character was speaking.

Bonus gravy points for "Nothing in your recording bothered me" or "your edits were inaudible--I didn't notice any big clicks or breaks" or "thank you for dividing that giant file up into four logical pieces (or zipping it all into one, or whatever)".

If you liked the reader's use of music--or appreciated there being no music; if you liked her inclusion or exclusion of things like author's notes; if you thought she used a good pace for the story; if her voice is just the right type for the story she chose...

There are lots of ways to think about podfic that aren't technical.

Oh, and if you think her particular voice would be fantastic for thus-and-such fandom or particular story, that would be a great piece of feedback.

Heh. As you can see, I have some thoughts on this!