Tried it last batch, and the upper temp never caught up with the bottom, which had the effect of making the mash sooooo long. I didn't try more than a 5F temp differential--just not comfortable with more. This last batch was a NHC round 2 re-brew, so I was trying to keep things mostly same-same. So, on a non-competition batch down the road, I am sure I will try it again and try a higher temp differential. Then again, my process is working without it, so also unsure what I gain by using it (other than finding another variable to fuss with that may or may not help the end result be better).
Speaking of, doubt I am the first, but I recently won two gold medals with my Gen4 so far, one at the ASH Cactus Classic in Saison, and the second at NHC round 1 in San Diego also in Saison. The machine works if I do my part!