The first time I had a chance to use it, of course I suspected it would have consequences. But after an enemy raid, a rather important colonist was dying and I had no other option, so yeah, I let the creepy stranger do his thing to her.

The colonist got a tentacle. She happened to have the body modder trait too. So, completely by chance, I gave a horrible, yet useful, mutation to a weirdo that was absolutely fine with it.