I have the NS200, and I'm really impressed with it, for the money, but I'm not impressed with the information given on the web site, or by some retailers.
First off, you need to check it will work with your current scope, unless you're prepared to replace it, as I had to !
You MUST have parallax adjustment, and it MUST be able to parallax down to at least 10yds, otherwise you won't be able to focus it properly. Also, some of the more expensive scopes won't work very well because of their coatings.
That aside, it's quick, & easy to fit, and set up. This done, the picture is very clear, with the brightness easily adjusted using the rotary switch on the top, to suit the distance you're shooting. I currently use it on a .22RF, and I'm not certain about shooting to 200yds, my longest rabbit is 92yds with it, although that was pretty clear. I think it will depend on how much ambient light there is. The darker the better.
It took a little getting used to, because it felt a bit like a video game to start with, aiming through the screen, instead of the scope, but there's no need to re-zero.
The biggest issue I had was ranging distances, although this will improve with experience using it. I made a point of ranging some land marks before it got dark, but found it difficult judging distances across open fields, because rabbits looked much closer than they were.
One down side, is the screen does of course give off some light, and this will reflect off your face. It took me a while to work out why some rabbits would look directly at me, not realizing how they could see me in the pitch black.
A friend uses a camera filter on his, and and this works well to restrict the relected light.
Mark.