I am not a translator, but I'm not entirely happy with any of those translations for Samsa's awakening. This one's (As Gregor Samsa woke one morning from uneasy dreams, he found himself transformed into some kind of monstrous vermin.) is the closest to what I read in the German, but ungeheueren is a lot more icky than just monstrous. It's something beyond that. But I don't know if I feel that way because I knew ungeheueren before I knew monstrous.