yeah, i wouldn't read into them too much, but i think over a period of time they are useful
if you look at CDIV and you see high % of shorts being opened, more buys (ask hits) than sells (bid dumps), yet the pps falls, you can assume a high amount of NSS
i get this conclusion from the fact that the demand is greater than the supply (more buys than sells, and shorts being opened to make sure orders fill). if D > S, than pps should go up, not down.
if the pps reacts as if S < D when everything else shows differently, than one has to wonder where the extra supply is coming from. that's where NSS comes into play, IMO.