I had some years ago. I found that it wasn't all that good for our very flat, thin flour gold that can float on water without using soap to break up the water surface tension. Our flour gold can take off like a piece of tissue paper in the wind with water turbulence in the sluice, so I ended up with unacceptable gold loss. Now, for gold with a little more density, it might work well.
I also did some math. Calculating the volume of those little holes on the dream mat vs. the volume of my drop riffles. I went with riffles because of the substantial increase of capture surface area. It allows for more gold to be captured and buried like in the real world, and many more traps to allow the gold to just "drop" as opposed to creating a reverse water flow, trying to get the gold uphill into that condensed round pocket. And, as previously mentioned, our light flour gold can take off like a piece of tissue paper in the wind.
