I have tried to embed audio in a post in version 3.5. Even scaled down and tried to use their basic theme, Twenty Twelve, thinking the theme I had chosen was the problem.
I am using a media host for the mp3 of the podcast (libsyn) and none of the ways I put it in the [audio] tag are working.
I even tried to the default m4a from the wordpress audio tag tutorial on the bottom, and nothing is working. Downloaded some audio plugins but they don't seem to be working in 3.5, so I deleted them and am back to square one. It's just showing up as text.