Honestly I don't know why there's so much said about the AI pro or con. I knew going in from what I'd read and seen that there was going to be a few diatribes both directions just due to the common problems devs face with deciding on basic AI mechanics in a game. Yes, game, that in itself means you need to account for things beyond Xenomorph lore to offer both suspense and survive-ability.
I think it's good enough that they manage to keep you on your toes. The Alien is never completely predictable, and he adapts to your tactics. That flare you toss isn't going to fool him every time. Conversely, if he could always track you by scent, it would always be "Game over!", as Hudson says. And if there were never any surprise attacks, you'd feel too comfortable.
I've been relying on frequent saves and the maps to test, then retry a segment that involves a lot of tough sneaks and pickup opportunities. It also is a way to go back and erase anything the Alien has learned about you. It's as well a good way to get to know routes and item locations for future runs on harder modes. In the process I have found the save reloads can result in many different scenarios as far as where the Alien is.
I'm sure they could have perfected a few things. Like taking a couple sec longer to optionally get in a locker more slowly and quietly by grasping it with one hand, then the other, gently depressing the latch, then pulling it open with your arm against it to muffle any noise. This of course accompanied with a variance in the Alien's detection level for each. The way it is though you're never sure whether it will find you in a locker or not, which again, adds suspense.
I don't think anyone's got the AI all figured out, and even if they had, I doubt Creative Assembly would say. The locker thing could be the Alien adapting, or smelling you if close enough for a certain time, or just a probability thing. It's been suggested by some that you're easier to smell in a locker due to being in a confined space while at times holding your breath, then letting it out.
If there IS a sense of smell that factors in, I would think extreme fear and breath at close range would be as much a liability as the locker is a safe haven. Prima Guide's info on the lockers in the game describes them as "both your best friend and worst nightmare". Personally, I prefer being under tables, desks and hospital beds.
I've played a little over 1/3 the game and have yet to use the hold breath feature, I don't even know how. I also read it takes health away within a few sec. This is one other common (and understandable) nit pick. Someone is going to find that script and change it from a few seconds to at least 30 sec before Ripley loses health holding breath.
Anyways, I don't have the flame thrower yet, and it seems even if I had it, I might not have enough time to aim and use it after jumping out of a locker. I suppose this locker stuff would add insult to injury for anyone that was a bullied student in their youth. LOL