Hi Steve,
I bought an early Monarch HG 8x42 and there is an unacceptable amount of CA centrally and much worse off axis.
At the edge the main deterioration of image is for me false colour.
I hope that Nikon can alter the glass mix or the separations of the lens elements to fix this.
Although mine might be worse than it should be.
Near the Sun, with the Sun behind a roof, mine has awful CA, but I wouldn't normally use it like this.
In addition when observing at night with a streetlight just outside the field of view there are many large arcs of ghosting or flare, although if the light is in the field things are fine.
I can see no way of fixing this. I think it is imperfect baffling in a small body.
My needs are clearly different to birdwatchers, as they seem to think the Monarch HG is fine.
Mine is a class down at least from the Canon 10x42 L IS.
Both cost me £800. The Canon is fully worth it. My Monarch HG would not be good enough for me at £300.
It does however, have a very bright view, and may have other attributes like focusing etc, which are of little concern to me, but may be important to birdwatchers.