Comparing root systems of live oaks I plant in diatomite vs. seed starting mix... ultrasorb definitely wins. Beautifully fibrous roots that have transplanted beautifully.
One of the things I really like about diatomite is that it mitigates the problems caused by a container that promotes circling roots in seedling trees. The roots lift free of the medium so easily that the whole length of unusually fibrous taproot can be extended vertically into the transplanting hole. I'm going to plant these trees at a local dog park, and I have high hopes
I've also used the very coarse optisorb to save another orchid. It's almost criminal how easy it was.