I'm thinking, that facing down is going to give an unflattering effect as far as casting facial shadows and harshness. I'm basing that theory on my photography knowledge. The worst time of day to take people pictures is when the sun is high in the sky. Unless you use a fill flash, you'll have unflattering facial shadows and the direct lighting can be harsh. The "golden" hours are the first and last hour of sun. The light is more diffused/softer. With the fixture pointing up, seems like the lighting would be softer and diffused AND you won't be seeing a "nekkid" light bulb :)
Monica

I don't think it will make the slightest difference in light quality. Just use a soft white or frosted bulb. Placement should depend on what looks best to you. If you have high ceilings, up might be better. If the ceiling is low, down might be better.

Have someone hold a fixture up where you're going to hang it. Try it in both orientations. One is likely to look better to you.