I have hada few problems with the durability of the Viper fiber optics. On 2 different occasions I had a fiber optic break. Other than that they are excellent sights.
Because of the 2 broken fiber optics I purchased a new Spot Hogg with the wrap and all I can say is that they are AWESOME. Bright, easy to micro adjust and rock solid. The only negative is the price, but you will only ever need one.