Are Holosun optics reliable enough to trust?

Holosun has earned a strong reputation — their better models (507C/508T, 510C) hold up to a lot of abuse and feature shake-awake and multi-year battery life. They're not quite Aimpoint/Trijicon bombproof, but they're close for a fraction of the price, and plenty of people carry them daily. For a defensive gun, choose one of their enclosed-emitter or proven open models, and always co-witness with backup irons.