The LA Times offers this report. It concludes with this from Bruce Cain:

While politicians debate the measure’s possible effect, many academics wonder if it would have any noticeable effect. Bruce Cain, a professor of political science at UC Berkeley, said he expected the major parties and big donors would adapt quickly and make sure they have only one credible candidate in each primary.
“As a social scientist, I’m glad that California wants to do another experiment; it generates more papers and more studies,” Cain said. “But I share the prevailing skepticism of my profession that any significant change will come about.”