So from what I've seen so far:
Seems to give you a free technique in your hand if you kill an opponent with perception-based techniques. But you need to do it in multi-opponent fights in order for you to be able to use the technique.
It does not seem to switch your offhand 100% of the time (I was Etheric most but not all of the time and didn't think to check if that matters). Looks like there's at least 3 more forms to find. I'm curious what happens if you make a 5-chain of one of each type of attack using perception? EDIT: don't think it's possible without venturing into unearthly territory.
(I bet it's not coincidence that Schematic Weakness comes out a couple days before, and is a rare perception based Melee technique.)