The difficulty is another thing I love about the game, I like a smart, ferocious alien. Though I'm a casual gamer, so It's not that impossible for me anymore. Still, the first few months when the game came out, I was getting owned constantly! It's not easy to get used to.
I like to play it with very low gamma, on Nightmare and with the Unpredictable Alien mod. The mod makes it more realistic for me at least, basically it allows the alien to roam more, but gets very aggressive when he gets close, and the less frequent encounters make me get a false sense of security and slip up more. It's AI is better than any jumpscare. Also it's very enjoyable to watch others play the game because of the unique encounters.
SM, have you played the Nostromo DLC Crew Expendable and have you gotten to the part where Dallas gets taken in the movie? That's one hell of a scene to translate into a video game, makes me tense every time.