i've been asking for it for a while now, it's good that it's there now. i've always used that paper for my things as it creates a deeper look and shiny brass. though i kind of wish the paper question page showed what the paper looks like because i know it doesn't look like paper rag - they all look the same on that page.
I, and I'm sure others, suggested having this option over a year ago...this is wonderful news! I used to order all my HDR prints from White House Custom Colour, because they had metallic paper. My HDR photos really "pop" on it. Thanks, Sean!
P.S. - I believe metallic paper is exposed paper, not inkjet.