Obviously, it depends.
But I wish developers wouldn't assume that a mute PC is automagically more immersive regardless of context.
In Half Life 2, for example, I just find it really distracting that apparently no-one lets me get a word in edgewise or cares what I think, even though they expect me to die for them. And why is this woman following me around and fawning over me when I'm clearly (involuntarily) giving her the cold shoulder?
I'd love it if in Episode 3 Alyx just grabs Gordon by the shoulders and shakes him, yelling, "Why won't you open up to me! I can't take it anymore!" And then it turns into a first person lawsuit for custody of Dog.