Siri doesn't do much well (besides set geo-fenced reminders), but the underlying technology enables a much broader set of use cases.

When I say "half-measure" I don't mean that Google Now is worse than Siri. I mean it's not really an all-out assault on the existing model of Google Search. It's more like a complement to it, rather than a disruptor.

A real task-completion engine would be disruptive, and not a half-measure.