The LA Times blog reports that, via preliminary exit poll data, "only about 1 voter in 10 said that his or her main motivation to vote in this election was Prop. 19." Most voters polled were mainly there to vote for governor, with 1 in 4 saying they cared about the Boxer-Fiorina race.
True, younger voters (under 40) were slightly more likely to say that Prop 19 mattered to them. Updates on the "semi-official" State Election Results page won't start for another half hour or so. UPDATE: The Chron is calling this for the NO camp, with 55% voting against legalization thus far.