Here is very interesting paper i found in podcasting over at Washington
http://catalyst.washington.edu/projects/podcasting_report.pdf

I must admit I think I have never listened to a podcast on my mp3 player. This is mainly because when I am commuting I like listening to music. Also since I have got a bike I find I am cycling most places, and this requires full attention

One of the perceived failures of podcasting initially was that the inability of people to get Rss feeds. When podcasting first came out I like lot of other people I suspect I subscribe to lots of shows with different topics and content, but soon found my hardrive filling up with lots and lots of shows.

I began becoming more selective and found that I listen most when I am at my desktop using it streaming from the sites. This same view was shared recently by paper which was undertook in Washington University. With 81% listening on there pc computer