Ernst:
I posted the same question on the Yahoo Groups forum, 'Digital Black and White, The Print'. I got a response back from Paul Roark that not only is he having great success with the RR-PPM, but he has developed a 6 cartridge dye-based inkset for it along with ICCs and ACVs. The ink set only requires Claria ink, Paul's custom dilution liquid (which you can purchase at inksupply.com) and empty cartridges. I have all but the dilution liquid, which I ordered, and I going to see how much of an improvment this makes.
I tend to make black and white prints on non-glossy paper, but RR-PPM paper really does make a great glossy image. I'll post results when I try out Paul's ink set.