After rereading Who Goes There and another more developed interpretation of it that's more similar to the movie (I love you that much more for writing a novelization of The Thing on top of Spellsinger, Alan Dean Foster) I'm reminded of where exactly my fixation on transformation horror came from.
The Thing is one hell of a mix. Not only is it visceral with copious amounts of body horror as the transformations occur, but there's also a focus on growing paranoia and the mental element of horror as well; the worst in everyone is brought out once they're cornered and emotions run high. Add in the isolated setting and the tension caused by no escape route and being unable to trust anyone or anything, and you've got a perfect storm.
There's something profoundly disturbing about being taken over from the inside out by something that violates both your body and memories and molds both as it pleases without caring for the significance either things had for you, and I feel the idea itself is just as taking as the movie or stories. I think that was why the short story hit me as hard as it did when I first read it: it was a blend of smart and grotesque, with room to spare for both physical and psychological mauling, and at that age I had never run across anything like it. I chased down the movies when I was older and could stomach visual gore better, but they completed my attachment to the idea and way of viewing--and later writing elements of--horror.
So if you ever wondered where lots of my ideas stem from, this explains a lot.