My two cents worth...I am currently using the Gold Cube to clean concentrates from my dredging operation. I have the 4 stack unit which has three trays.
A. The Gold Cube appears to live up to the claims its makers claim. I can not report on the actual percentage of recovery yet as I haven't performed my "scientific" test yet, but visually I would say it is true or pretty darn close.
B. The gold we are getting is small. Minus 10 mesh plus 30 is 2.375%, -30 +40 19.938%, -40 +60 33.217% and minus 60 is 44.47%...so pretty small stuff.
C. Of the gold the Cube is recovering for us, probably about 85 percent is on tray one; and 15 percent on tray two. Rarely do we see any gold on tray three.
D. We have panned MANY buckets of "tails" with only the occasional pieces of gold found, so no it does not get 100 percent.
E. The feed rate is pretty good. We feed a 5 gallon bucket in about 10 minutes and it appears we could feed a LOT faster, I just don't like to feed cons so fast.
F. Though some people on other forums have commented on how expensive the Gold Cube is, I can only guess that they have never been involved in manufacture/retail before. There are a lot of costs that are factored in to a retail price. The cost of R&D, molds, and other expenses need to be amortized into the price based on an expected product sales lifetime or "How many of these darn things will I sell." Let's face it, Gold Cubes will never sell as many units as an iPod so the amortization of expenses cost will be higher. The components such as bilge pump, hose, steel frame (nicely done by the way), are priced very much in line with other mining market items. The Vortex matting is EXPENSIVE as I have found it available on the internet already from a couple of different sources. So, when you add it all up, the Gold Cube is a reasonable value.
G. I used to own Armadillo Mining Shop, but no longer sell any mining equipment...including the Gold Cube, so my observations are not self serving as I am not making any money from increased sales of this device. Is it perfect, no. Can some extra features be added , yes. Would I recommend it to my best friend to buy one, all ready have!
49er Mike