Baring only a slight comparison to the e.l.f. HD powder this mattifier comes in both loose form and a pressed powder compact. I have never used the e.l.f. HD powder or any other cosmetic product of its kind but from having seen pictures and reading reviews I can gather that they are ranked highly, particularly the MUFE HD powder-though I have no experience with any of them the texture and purposes of the products seems comparative.
I like the Black Opal oil blocking powder. It is very finely milled so it does not have the cornstarch feel and very much disappears into the foundation. I use this to set under eye concealer and often times the t-zone which is the area that usually gets very oily.
I wouldn't say that it is special or that it is on par with the others since beyond texture (which is a mere estimation from the pictures I've seen) I know nothing else about the MUFE or e.l.f. HD powders. Too much of the Black Opal oil blocking powder can cause a "cakey" look and feel. It absorbs oil and is pretty much colourless so you will not have to worry about the white cast normally associated with these types of products (unless you use too much). It looks good on photographs no ghostly hues to worry about if you should be caught on film unawares. It's effect is not sustainable and you will have to reapply readily to keep your face oil free and matte which I strongly advise against primarily because it will get "cakey" and settle into fine lines, wrinkles and pores.
It is a handy cosmetic, but it is not a necessity, you can live without it! I do prefer to press and roll it into the skin with a cosmetic wedge or powder puff as I believe this gives and enviable finish. I recommend using with a light hand to avoid "cakiness" and ghostly/zombie mom appearance.