Great plugin, nice and clean. A couple of suggestions:
1) Is there a complete listing of the shortcode options somewhere? Are url, dl, and text the only options available? I'd like to see some additional options that would allow me to set the formatting for an individual link, like fs="12px" if I want to set the font size for a particular link to 12px, but keep the other links the default size.
2) The progress bar seems to depend on the length of the text. It makes it harder to exactly position the slider on files that are long in duration but where the text is just a short word. For example, if I have a recording that's 45 minutes long and the text is Play, then it gets really hard to position the slider to, say, the 10 minute mark unless I lengthen the text to Play this long file to generate a longer progress bar. I'd like to see an option where the progress bar can be set to a specific number of pixels. It would also give the progress bars a more uniform look when I have multiple recordings clustered close together.
By the way, I haven't had any problems using recordings other than 44100 hz; I've got MP3s at 16000 hz & 48000 hz, and they play just fine.