Mine has updated but I've not noticed any difference with the Immersive Sound.
Which inputs is it most clear on?
To me... All I have noticed is the auto setting which varies the amount of effect applied. But the actual effect based on the level selected has no difference at all.
So I don't think there is audibly any difference whatsoever, just the ability to auto adapt the level based upon the type of music/audio being played.
But I may not be the best judge, I'm not fan of playback audio processing, I like the sound to be as pure to the original as possible.