Lol i don't understand how all you guys aren't affected by this. It's just weird! I like it for Sigourney, that's not the point. But i still think it's just weird and confusing of having the biggest (human) character ALSO voice - quite recognisable - a computer. I don't know, it doesnt fully bother me, but it just feels like a weird bump in a otherwise smooth and well executed plan.
but hey, i'm bringing way too much attention to this rather minor detail. let's just forget it.