I have used one.
Obviously it needs higher than usual mounts, light transmission is extremely good.
Can't say it was a huge difference over the 56 but, it was very good.
For me it was just too much scope for a stalking rifle, I imagine if you do a lot of fox or Boar shooting under moonlight from static positions it's an awesome tool.
If you can get one cheap enough, certainly worth trying.
Atb
Moses