OK, here is my experience after almost one year…
First, I purchased Darrell's ART for a Schmidt-Bender, which has an extremely high price/quality relationship. It is my understanding the Germans may hunt at night for deer in the Black Forrest so they have developed a tube with lens that are capable of night viewing, I presume with full moon conditions. Secondly, the Schmidt-Bender has the reticle located in the first focal plane.
Secondly, anything new to me is confusing. I am NOT one of those people who can read a manual or listen to a presentation and Viola! All is understood. It never happened in grade school, college or anywhere near the present.
Mind you, I had zero shooting experience at any range beyond 100 yards at mostly White-tailed Deer or jackrabbits as a child. In my research before purchase stage, I was not convinced this ART was anything other than a gimmick. I knew I wasn't shopping for this thing at Wal-Mart and it wasn't priced accordingly. Really, I had little experience at shooting a rifle but had considerable shotgun time over my Brittany's hunting quail in South Texas.
With a small learning curve, I now have index cards I have duplicated the ART onto as well as ranging sizes for various wild animals. E.g., coyotes, deer (doe & buck), and even turkeys. I have spent a fortune on a few rangefinders and all have their limitations. Also, they are slower and at longer ranges or not effective or won't return a yardage at all.
If a turkey crosses a sendero (Spanish for fire break) at some undetermined yardage, I merely get my rifle in position and range it with my ART system. I simply hold the ranging card (printed on the reverse side of my reticle image) in my right hand (I am left handed) and look at the subtending angle and within three seconds I have a yardage to target. If in this example, the turkey was a doe I wished to cull, the shot would have been off within a matter of 15 to 30 seconds as compared to aiming a rangefinder, acquiring a yardage (hopefully it will work in low visibility or light conditions), putting the rangefinder down, picking up my rifle, getting it on a rest, blah, blah, blah. In the least, I would know a range to a known point. I scratch that down on a blank index card mapping the area.
You get my point.
As far as MOA v Milradians, here is a simple way I understand it; 1 Mil = 3.438 MOA. Or, put another way, 1 true MOA subtends 1.047" at 100 yards, whereas 1Mil subtends 3.6" at 100 yards. Mil's are accurate, MOA are super-accurate! If you wish to witness the potential error go out to 300 to 800 yards and it all becomes very apparent in a hit/miss scenario. If you have a rangefinder which will give you immediate and accurate ranges from 400 to 1000 yards, you probably have little use for the ranging function of the ART system.
Finally, making the actual shot is literally a no-brainer for a no-brain like me. Range it with the ART, never put the rifle down or off its rest, look at your index card, get set on your rifle (you already know by the index card what the MOA holdover is and simply make the shot. Your confidence is maxed out. You know that bullet will arrive at its intended destination. It is a wonderful experience, each time!
With Excel and a few index cards you can insert other sample targets to range for your hunt or ranging practice. With the height of telephone/utility poles, unoccupied (remember the "do onto others…" thing) trucks/ATVs, unoccupied hunting stands, livestock (cattle, sheep, goats), rabbits, ravens, buzzards, gas pipeline markers or risers, water troughs, windmills (or sections) etc., you can simply create your own quick reference cards. Even fawns are useful at a particular time in the season (therefore average height) is very valuable.
A friend told me of an experience of reverse-ranging a caribou's antler height and knowing the distance by ranging adjacent caribou, he could get an accurate idea of the antler height (beam length) of specific bulls lying down. He could better estimate a B&C score with the ART.
If you are shooting up to 300 yards in known yardage conditions I am not sure the value of this reticle system if one knows their rifle's performance.
There is a downside to everything…the yin and yang thing. Once I purchased one of these darn things and used it, learned from it and with it, another rifle in my safe begged me to put one on it. I am slow, but I quickly figured out two of these things are twice as expensive as one.
Go shoot!