Hmmm, I like Neopan 1600, too - but only shot at around 1000 ASA - it gives a certain melodramatic look to pics, kinda like from 1940s/50s film noir movies - I think this is due to the rather high contrast of the film, and the poor shadow definition, and could be used as a special effect; at 1600 and upwards, contrast gets pretty hard to manage with NP1600, though, and there is almost now shadow definition any longer - for that I much prefer TMax 3200 (at 1600 to 3200 ASA) - much grainier, but also much more shadow definition and easier to deal with, contrastwise; never cared for Delta 3200 - has finer grain than TMAx but, my results with my developers were always less sharp and defined, kinda washed-out...
Roman