As much as I want to like this feature, I've found it less than impressive. It rarely picks me up on the first try, so I find myself shouting a very clearly-enunciated "HEY SIRI" a few times, which kind of kills the magic. About 50% of the time I just end up walking over to the phone and using my hands to accomplish whatever I was trying to do. I'm not trying this from far away or in a noisy environment, either. Admittedly an anecdote, but still frustrating.