I've seen similar results as Nelson. I've been moving my bag rooted cuttings into 1/2 Pro-Mix BX, 1/2 Napa floor dry (diatomite), and the roots are looking much better than the same cuttings put into half and half perlite/vermiculite. Also, I was having trouble with moisture regulation of the perlite/vermiculite, and lost too many to rotting or desication. Now the cuttings are producing abundant white, thick roots. I think the mycorrhizal fungi are partly responsible for the improved success. It is supposed to help with disease control and improve root development. The diatomite is also probably helping. It is supposed to be one of the better mediums for hydroponics due to the excellent water and air storage, and also the silica it is composed of.