[Quarkboy]

For interested people, I used the -nr parameter in my latest release of Sugar sugar Rune 03.
It might be a good idea for someone to compare with episode 2 (which did not use it).

From my experience so far, with a strength of 100-200 there's very little visible difference, but a bitrate savings of up to 2% on a DVD-raw based anime source. For a really noisy source, it had much greater savings, nearly 10%... however it didn't really denoise well, so what would probably happen would be a series of filters before the encode that would already kill most of that noise anyway.

In any case, as far as I can tell it looks like free bits to me, so there's no reason not to use it at low levels on all encodes (it doesn't seem to slow down encoding much at all).