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Jelly Bean is available (at least for Galaxy Nexus owners) if you have unlocked your phone and don't mind playing with non-official ROMs. I won't post links here, it doesn't take much Google-fu to find at least two different builds. Now is really nice, so far. The natural language parsing seems very robust. It doesn't seem to have Siri's sense of humor, which is a mixed blessing.
11 months ago on Google Now Official Landing Page Now Live, Ready For Your Thoughts