Why ever use 1600 or 3200? It's obviously not as 'good' as 100...
My point is the fact that 1600 ISO isn't as "good" as 100 is obvious to most people...that 50 ISO is sometimes worse than 100 ISO is certainly not as well known.
I'm still not sure why you'd go below base ISO under controlled (ie w/flash) circumstances since it can lower dynamic range...seems you'd reduce/diffuse the light to keep ISO at or above base.
At any rate, I'm just glad to know the Lo settings on my Nikon are not necessarily where I want to be.