People certainly do this, as RA-4 paper and processing chemicals are not expensive. As they mention on hte site, the paper can be reversal processed to make a positive. I have seen this once before; the colors are ot exactly perfect, but its a really cool effect.
It's cheap; 100 sheets of 5x7 Kodak stuff is $15.95 at B&H.
I'd imagine that you could even cut down a paper roll and put it into a rollfilm camera; wouldn't that be neat... though exposures would be lengthy, as I'd assume that the paper is close to B&W paper's speeds in the ISO 1 to 5 range.