I have never even tried to use them... they seem horribly weak and difficult to use to me. I suppose that one would be reasonable for use against Zombies, and could have other misc. uses however given their traits.
I have heard of one person who has had some success with a mix of Psylok's and Thoughtspores, though... I just don't know any of the details.
EDIT: Removed comment about Zombies... forgot the attack was psychic.