Go throw a few of your favorite artists tracks in mono and see how much it affects their sound, and then shoot for that as a goal.  In general your mono compatibility has to be good if you ever want to play live. Look into which effects and panning techniques that you might be using that aren't so mono friendly, and then learn some alternative ways to get that sound. If you really want to push yourself, produce your whole track in mono, and then go back and add the stereo effects at then end, it's like magic.