To clarify, once you test how it reacts to your weapons, if you really can outrun it, how it looks for you when hiding (usually only when you make too much noise or get spotted), and how hiding spots work (hint: at least on hard mode, the alien will always check lockers if you hide in them for too long, but under desks or behind stuff? you're gucci my dude ), you'll never ever get caught and it just becomes a tedious slog of sneaking from one place to the next and hiding when the alien becomes active.
Also, the graphics are so good, that little things like trying to shoot the aliens knees and having it charge ahead at full speed, completely unhindered, was a bit annoying. I don't care how bad ass an alien lifeform is, nothing is going to be running after a point blank .45 magnum to the kneecap. But I really can't complain about it too much, just a personal gripe.