I'm a pretty heavy user of Siri, and did get the 4s specifically for it. Mostly for reminders, but it's also very useful when riding a motorcycle (directions/text messaging). All 3 companies are making some good advances in the voice recognition area, including the context aspect. Android L is gaining the exact reminder features that had me buy a 4s, and Cortana has added some nice features in that area.

Though the Jibo reminded me more of the other aspects of a personal assistant, distilling a flood of data down to the important and relevant parts. I see Google Now ahead here currently, though Microsoft has made some interesting advances with Cortana, and Apple is starting to close the gap with changes in iOS 7 and 8.

There is a creepy feeling aspect that comes from these features though. Tony and I used to go to a particular lunch spot frequently. My iPhone started showing traffic info there automatically around lunch time every Monday. The creepiness is starting to wear off for me, and I'm curious to see where this goes in the future. Especially for families.