I'll try and find the pic for you of the root system but have no doubts about it, it builds one hell of a root system as the perlite retains oxygen...you can always go 3 parts perlite 1 part verm, i know people have used 100% coco too and have nothing but positive things to say. as soon as i find a good pic ill post one for you...

All in all though its a good, easy method and its nearly impossible to damage your plants from overwatering this way...