I personally tend to pronounce it two or three different ways, depending on how I'm feeling. And in mythos stories and adventures, my preference is for characters to almost never see or hear the name in its "orthodox" form and spelling. Having it highly altered adds to the sense of folklore and incomplete human knowledge. After all, it's not like "Nyarlathotep" is the name his momma gave him; it's just a persona the thing put on back in Egypt one time.
Not that that's relevant to a new scenario I'm currently writing...not at all.