Breathing Color sent a trial size 17" roll of the Vibrance Metallic 255gsm paper and I've finally made some print samples. I used the Epson 4900 with BC's canned profile, and the Epson Premium Glossy Photo Paper media selection in the Epson driver. The profile seems rather good.
I can't tell if this is the Mitsubishi paper or not, and my only prior experience with inkjet metallics is the Red River branded Polar Metallic. To my eye the papers are similar to one another, but I'll need additional time and printing test to talk about differences between the metallic's made by BC and RR.
In my view, I'd encourage anyone interested enough to read this to try at least one of these papers and see for yourself if you haven't yet, as I'm glad I did. While the pigment inks laid atop a reflectance layer can probably never reproduce the Kodak Endura result, I still feel it's of value for certain images. In my hands, the metallic inkjet papers shine when Dmax and gamut are a priority, and I'll say that subjectively each of these eclipses my usual paper when these parameters are a priority, Canson Baryta Photographique. But the property of greatest interest is the appearance of depth, and this is most expressed by high-key content. I suspect this is as simple as smaller doses of pigment being laid down in such image areas, and as a result, the opacity of the mask preventing light from making its way out from the reflective layer is reduced vs. densely inked areas.
I'll add that this 3rd dimension is most apparent if the high key areas have some decent high frequency detail. Some recent print work has, for example, tack-sharp water droplets streaming off a black wetsuit worn by by swimmers, and this paper really makes it quite a sight to behold.
Scott Martin mentions above possible value in either a gloss optimizer or a face mounting. Since some of my metallics have been informal gifts, I have used a glossy laminate to face the print after 1/2" Gator Foam mounting. The glossy laminate is something I'd never use for a serious print, but it does - at the minimum - not detract from the sparkle and pop that these metallic high-key high DR prints have.
So while my comments are purely anecdotal and are badly quantified, I'll just offer that the inkjet metallic process holds my interest from some subjects. Since I've given up resenting the papers for not giving us what Kodak Endura did, I'm enjoying what they do offer. In my book, purist or not, there is a look that I don't think we can achieve any other way right now.