I have an ATN X-Sight II HD. Have had no issues with it. Right off the bat I started using the big external battery (a must have) that is recommended because the scope is a power-hungry beast. Don't even think about operating this scope without the external power pack! I love all the features of this scope. The advantage it has over the Nightsite is that it doesn't illuminate your face and make you more visible to your prey. It is sensitive enough that you can sit in total darkness and see just fine. On extremely dark nights, the infrared illuminator offers daylight conditions and your prey cannot see it. Further, you look at the display with only one eye, and your other eye remains useful for night vision. It's very heavy, as you probably already know. But it's worth the extra weight if you're going after night-time predators and pests. Mine is full time dedicated to my AirForce Condor .25 with bi-pod and I shoot off a bench for coyotes that I bait into my kill zone. I rarely miss! Lots of coyotes in the bag. If something bad ever happens to this thing, I'll immediately order another!
The downside of the ATN X-Sight is not necessarily the scope; the problem is with the writers of the operating software. But they're slowly getting the bugs worked out. I don't have the latest software downloaded yet and am using an older version that meets all my needs. But when I upgrade, I should gain the use of the bluetooth feature and GPS and other goodies. But all I really use is the night vision. That alone is worth the money for me and many others too.
One last note: I have used this scope for daytime testing and target shooting. It's not as nice as looking through a fine piece of glass; but honestly, I don't know why anybody would complain about it for daytime use. It's really quite good in my opinion, especially when fitted with the front lens restrictor.
Hope I've helped.
BeemanR7