So far, I have had no bad experiences with such a set up. I use the MUM gen3 with a universal adapter setup on my 22mag bolt gun (primarily), AR carbine, 10/22 (lots and lots of fun w/ a silencer), and have also used it on several of my buddies' guns. With my AR I have been able to CONSISTENTLY hit milk jug sized targets out to 200+ yards. I'm fairly certain that I could go further, just have not tried. The range limitation, for me, came from the IR illuminator I am currently using. God forbid you are someone so lucky to have some sort of laser illuminator I have a feeling your range would be limited by the caliber of the rifle only. I have used it in passive mode (no illuminator) but it is not as impressive unless the moon is out. In starlight, it still works well w/o illuminator (on my glass at least), but having an illuminator on makes a HUGE difference. Yes, eye relief can be an issue if you let it be. Most of my stuff is not uncomfortable enough to warrant doing anything, but if it is, throw an extra butt pad onboard... problem solved. On a nice day scope, these things really kick ass, but mine even performs well on my bushnell cheapy and simmons super-cheapy. Would not use it behind an illuminated reticle day sight unless said sight has been designed with NV in mind (ex. eothingy, aimpoint, some version of the shortdot i think too). For me this setup makes a whole lot more sense than a dedicated riflescope, which i had tried and realized that i barely shot the gun anymore since it was only for night time. I love the hell out of my setup. Works well to have a spotter NV to use apart from the weapon mounted one, but is not absolutely necessary. I'll stop ranting...