My "enformation" is that the jack works fine, with the supplied earbuds, iPhone earbuds, or almost any third party earbuds that have a mic.
But while inserting the jack its possible to trigger silent (mute mode) or start/stop the music player accidentally, and its easy to put it in not all the way.
If you ever got your headphone wet (mine went thru the wash) they may not work after. (Mine did - amazing).