Obviously, the experts are saying podcasting is growing by leaps and bounds.  Here are some figures in the Bridge Ratings survey found at MediaPost:

5 out of 300 have downloaded a podcast
20% of those people listen weekly
the average user downloads 6 podcasts and spends 4 hours listening per month
only 20% use the MP3 format to listen
by [...]

Because podcasts are difficult to measure in terms of statistics, Audible is rolling out a measuring tool aimed at podcast publishers who want to secure advertising on their podcasts.
The new service IS innovative, but because of several factors is not one I would recommend. 

It changes the file type to .aa.  This file type is [...]