I've got a Grizzly pan and Gold Miser mini-sluice.
I don't care for it, I'm sure it's faster at pure concentration of black sands but overall it's awkward.
First of all you still have to do something with your concentrates and that "something" isn't going to happen in the Grizzly pan. I suppose that's why you get a mini-sluice, but any speed you picked up is now lost feeding half teaspoons into the little sluice. Besides who doesn't like to "peek" a little when panning

No peeking with the Grizzly!
Something else that rears the head of gadget disappointment is the lack of utility of the Grizzly pan. Think of all the other things you do with your traditional gold pans, how nice and steady they sit there while you clean a hand sluice into them, or have it sitting next to you crevicing with a classifier on top. Sitting next to the high banker so you have a handy place to throw an interesting specimen. Soaking clay balls, soaking your feet, hell the list goes on and on.
Den