If one is flying IMC.....there is scant need for the nightsun to be operating.
The 412 has to have overhead curtains for IMC flight due to a concern about "Flicker Vertigo" thus it would appear there are many aspects to Instrument Flight that have to be considered.
From a personal perspective....the nightsun is a great improvement for night scene landings and if combined with an IR lens and NVG's.....really makes night scene landings a whole lot easier and much safer.