Maybe I just haven't figured out how to use it but I do not see that it is very useful. Just about everything you ask Google Now opens a Google search results page. You cannot ask it send text messages. You cannot ask it to read text messages while driving. It seemingly pulls traffic when going home even when I am driving in to work. It has the wrong time most of the time. If I activate the button on my Bluetooth ear piece, it opens the regular Google voice search instead of the Google Now interface which seems to be different.
I honestly do not see what it is for. I removed the Robin app because I thought Google Now would replace it but maybe I am wrong. Yes, I have JellyBean on my Galaxy Nexus. Yes, it is nice. This feature however isn't very useful so far.