there is no problem with the plugin as such but the author should update the documentation with clear installation and usage pages, the html5 player is good looking, it would be good to post screenshots too.
not everyone is a plugins guy, the kind of ease wordpress provides should also echo in the plugins. help those who need help, my kind!
audio shortcode can be used, [audio]
however it would not accept url other than media library, simple [audio] addition would list the mp3 files in your media library.
there is a need for adding titles, artists as parameters adding these would help popularize the plugin.
use audio-player and for using it see http://wpaudioplayer.com/frequently-asked-questions/