I have 4 of them that I use for Steel Challenge and IDPA. They’ve worked fine over the last few years.
Okay, my only real issue with the Holosuns is that the vertical and horizontal adjustments aren’t [ahem] linear. No real big deal given that you don’t adjust the zero for different distances.
I have switched over to HE507comp-gr sights. On my 22 rifles I use a lower 1/3 height mount. Several observations on the new sight. First, my eyes like the green reticle a lot more than the red. Second, I’ve found I like the 32 moa circle/dot reticle better than the 62 moa circle/dot of the 510. Probably just personal preference, but worth noting.