I haven't used it on a model 77, but I have a NECG peep sight that I had mounted on a Ruger No.1 as a back-up for the scope which was my primary sight. Once you get it sighted in (and you should read the instructions on initial mounting and sighting-in, despite how easy it looks) it goes on and off with no effort and returns to zero well enough (within a MOA). It's nicely made and finished, and doesn't look too bad. It attaches with a large knurled bolt, which makes it great to throw into your pocket and quickly install without tools if needed...much handier than a spare scope, which will be back at camp rather than right there when you need it.
If you're talking about using it as a primary sight, the only downside I can see is that it isn't particularly attractive, especially with the clunky mounting bolt head sticking out the side. Also, once you get it sighted-in it holds the setting very well, but if you anticipate doing a lot of sighting changes for different loads, you might want to look at something else. It isn't click adjustable, has no reference marks. It isn't readily re-sighted, either in the field or at the range.
John