Even a cheap, utterly inferior NVU puts you entirely in a different world at night.
I was able to slink around in diffused moonlight, about fifteen feet behind an enemy squad, shoot half of them in the ass with my Skorpion over about ten minutes' time, then knife kill the rest of them.
Then I danced around like a dumbass because nobody else could see me, not even DT's crew with their own NV unit.
It's important not to use gen-0 or active infrared unless it's absolutely necessary. These things WILL give you away to anyone else using NV or IR.