I find Siri mostly useful for things like taking messages and playing music when my hands and eyes are occupied with other things, but as many people have pointed out, figuring out what exactly one has to say to get Siri to do it's thing is often hard, even when you realize you've got a parsing problem. I mean, ever try to get Siri to play a song by "Them"? Unpossible by band name. :/ What I wouldn't do for a manual or keyword guide...