An example of how good/creepy Google Now is.
My friend Jen was coming to visit from SLC. Google Now told me her plane was 24 minutes from arriving at the gate at JFK. I had never told them she was visiting me or what flight she was on (I didn't know). But they did. Probably because she uses Gmail or their calendar, and somehow connected me to that trip (or did they just guess!) and thought I might be impressed if they told me about her flight. I was!
And I felt a little nausea, as I realized they have me by the balls and don't mind if I know it.