I use Siri regularly, but only for things like this:

- "timer, 10 minutes"
- "remind me tomorrow at 10 to pick up blah"
- "where is Eryl"
- "wake me at 9"

It works very well for me for those sort of things, it is hopeless in the car. It needs the fast speech recognition that Google have to make it more responsive (there are some improvements in iOS 8, but still not as good as Google in that respect).
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Remind me to change my signature to something more interesting someday