Indeed, spoken output is great - in theory.
But unfortunatly (as many things done by apple) their effort is minimal to make their "great innovation" multilanguage.
"The main advantage of it is that it allows you to read text in many languages."
This is not an advantage, it is a pure base condition if want to work with that feature (the quoted sentence above is somewhat arrogant, you maybe want to imagine, what happens, if apple forces YOU to speak/write in german only to make some of the features work. Crazy, isn't it?)
I'm living in germany and so speakable items is junk to the same degree that the speak synthesis does not work for me. If you know more than apple, then you realize, that this is true for the great majority of the european continent (if you know much more, than you realize, that this is very true all over the world).
This is the reason, why I'm not using it. Maybe apple will correct their behaviour (very unlikely) and start with spoken interface their apology to all not english and not japanese speaking people on the world (I only believe this, when I see that, not even a petasecond earlier) but...