QTR-Quadtone RIP

I expect this has been asked before, but how do people like the Piezo  
inks compared to Epson's Ultrachrome?  I used the 4ink piezo setup in  
my 1280 for years.  But since my 4000 came with color ink I tried  
that out with QTR and have been quite pleased, especially with the  
ability to fine tune the warmth of my prints.

Are the carbon pigments of Cone's any more archival than the OEM stuff?

Other considerations?

Thanks,
Chris