PPIC has issued this report by Eric McGee and Daniel Krimm. Here is the summary:
In the June 2012 primary, California tested two important electoral changes: new legislative and congressional districts drawn by an independent citizens commission and a “top two” primary system. The results suggest the reforms produced some changes—in particular, more open seats and more competition. However, there was also a great deal of continuity with recent elections: most candidates endorsed by a major party and all incumbents are advancing to the fall election and partisan outcomes were broadly in line with what might have been expected under the old primary system. Over time, the reforms may produce more radical change, but the first step on the road of reform has been a small one.