I have shot the Horus H25 extensively for over a year, on my .308 AI-AW. The scope is a USO SN3 3.2-17.
The Horus reticle shines when you need to engage multiple large targets from 300-700 yards,
in my opinion. The benefit to the Horus reticle is getting rid of the need to dial elevation (or windage), so it starts to be useful beyond the point-blank range of the cartridge (say 250-300 yards). Because of the reticle line thickness and general "busyness" of the reticle, it is most useful on large targets, such as IPSC silhouette targets.
When using it on small targets, it can be difficult to get a good sight picture due to the line size and target area being obscured by other parts of the reticle. The smallest/furthest target I have been able to engage with the H25 is a 1 MOA plate at about 700 yards. Anything smaller or further, I cannot resolve a sight picture.
The Horus is most useful in multiple-target engagements, when the time it takes to dial elevation would be a liability. If you are not under time constraints, you might as well dial (and I still often do with the H25) . For the time advantage to be effective, you also need to have your dope memorize.
To convert dope in MOA to dope in mils, simply divide every "MOA" value by 3.43.
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