I ran through about 10 x 30m bulk rolls of that film from 2006 (ish) through to about 2013, all bought at the same time. I have about 5 rolls left, out of the 180 roll initial purchase.
Shot it almost exclusively in winter on rainy, cloudy, not so bright days. It has great contrast and certainly snaps a picture up.
I always developed it alongside NP400. I just went to my darkroom and looked up some details. In 2006 I developed two rolls of NP1600 alongside two rolls of NP400 in D76 1:1 for 9"30" at 20ºC. My notes mention beautiful negatives from both films.
In 2008 I developed three rolls of NP1600 along with one roll of NP400 D76 1:1 21ºC for 9"45". Notes mention the NP1600 was brilliant, NP400 not too good.
In all cases I exposed the NP400 at 320 ASA and the NP1600 at 800 ASA.
NP1600 was designed to be developed alongside NP400; something I was not completely convinced about. One test roll later and I was a convert. Wonderful film, but it is a very contrasty film and really is suited to low contrast shooting conditions where a snap is often welcome. Unreal grain structure as well, makes brilliant winter condition prints look fabulous.
Essentially, exposing it at 800 ASA then developing normally for it's 1600 ASA supposed box speed, worked brilliantly for me.
Mick.