A quality receiver sight makes it a whole lot easier for me to place my shots more precisely, especially out at 100 yds and better. IMO, this will hold true for most folks once they try them.
The photo appears to be a Williams GRS (Guide Receiver Sight) set with the Firesight FO front. Williams has a couple of other options that're no-gunsmithing items: The "5-D" which is an "economy" line with no micrometer-click feature (GRS has similar adjustment set-up) and the "Foolproof" with micro clicks. All have easily replacable apertures in various sizes, including the "Twilight" series with a brass insert around the aperture for faster pick-up in low light hunting situations. I have some version of all three on various rifles and carbines, and they all are well-made, sturdy and precise.
The Lyman 66 series is also made in a version for the 336. It is all steel, and a bit smaller than the Williams FP and 5-D, which is why I like it on compact carbines like my Rossi 92 "Trapper" in .357. Another time-proven design, and very well-made in the USA.
There are several other more recent options such as the Wild West Guns and XS models mentioned. From my limited experience with these, I'd favor them more for fast shooting at close ranges, as for dangerous large game or "social" SD situations. Personally, I can do a lot better with a smaller aperture, especially at more extended ranges, and like the option of being able to try several different sizes in order to find the one that gives me my best compromise of speed and precision on a given weapon.
Whatever option you choose, I think you'll be pleasantly surprised with how well they work and how much easier they are to shoot well with.
