Having used up to the AN/PVS-7 Generation in the Army, I honestly didn't expect much from the Yukon Gen I. I was very pleasantly surprised. As long as there is any kind of ambient light, it works very well. With focus adjustments on both the ocular and objective lens you can fine tune for a crisp and clear picture. Livestock in an open pasture are visible to 200-250 yards. The IR illuminator is quite good too. Most IR illuminators just kind of give you a low wide-angle glow on the ground at your feet. This IR is more like an invisible spotlight. I don't know the exact range range, I'm guessing around 75-100 yards in the open, and it is like shining a 4-cell flashlight into the really dark and shadowed areas you can't see into in the passive mode. A tad bulky in size compared to many monoculars, but quite light in weight.
The plastic body seems a little flimsy, but I must admit mine has seen a considerable amount of field use with no problems or damage. My LEO co-worker likes it a whole heckuva lot better than the big heavy old surplus AN/PVS-4 they issued him.
My only real big complaint is that there is no way to adapt the monocular to anything else; you can't mount it to a camera, camera tripod, head harness, etc.
In a tactical situation the glow of the control buttons' on-off indicator lights, as well as the green light shining on your eye socket from the ocular would give you away to anyone out there looking for you with night vision devices of their own; a rubber eyecup and some duct tape would cure it, though. This was not intended for military/tactical use anyway; just a note on things I have observed with the unit.
Still a very, very good deal for the price tag IMHO.
Pros: fairly small and light, relatively low cost, very good performance for Gen I
Cons: No good way to adapt to other uses
This review was written in the old system and had content requirements that are different than reviews written today.