I have had a Warthog for a long time. I know that it is not up to date and certainly not an A4!
But, I will give you my opinion that I think will apply to the current versions.
I usually only use mine for kitchen knives. It is works, but it is kind of clunky. Unrefined.
It is a pain to change the diamond stones. I have two sets of them, o believe that they are 600 and 1000. But, I could be wrong! I start with the 600 and do all the knives that I want sharpened. Then, I remove the two sides of stones and mount the other set. It involves using a screwdriver and takes a lot more time than simply tightening a stone to a holder.I use 20° or 40° inclusive.
It does hold the sharpening angle and you don’t flip the blade. You push down while drawing the knife thru. I don’t go back and forth. I don’t like pushing forward while pushing down. I only go from the heel to the point-or pulling while pushing it down.
The biggest issue that I have with the design is the amount of pressure that you have to use while you pull it. You can’t really adjust to a lighter pressure, so it is aggressive and prevents using a touch to remove any burr. You need to use a strop or hone to finish.
I would not buy another one. But, it works for many folks. I prefer my Sharpmaker for touch ups, and my KME for serious sharpening.