It's fairly rare that you see the California Court of Appeal disagree with a justice on the California Supreme Court. But that's exactly what happens here.
Admittedly, the opinion by Justice McConnell merely says that the California Supreme Court's decision in Alternative Systems remains good law even after the Court's subsequent decision in Aguilar. That's not really a bench slap to the California Supreme Court or anything. Nonetheless, since Justice Chin exressly concurred in Aguilar to argue that the majority decision overruled Alternative Systems, and since Justice McConnell's opinon states flatly that Justice Chin was wrong, it's still pretty bold.
Justice McConnell's holding, by the way, is also fairly important on the merits. She essentially concludes that arbitration clauses in attorney fee agreements aren't effective because the client can still request nonbinding arbitration under the Mandatory Fee Arbitration Act and, subsequently, a trial de novo in front of a jury. The client will have to jump through a few hoops first, but that's nonetheless an effective way for the client (but, I might add, not the attorney) to get out of a mandatory arbitration clause. Those California attorneys who put arbitration clauses into their fee agreements might well want to keep that holding in mind.
At least as long as it lasts. My take is that the California Supreme Court should (and probably will) take the issue up at some point, perhaps even in this case. They gotta decide at some point whether Justice Chin is right that Aguilar overrules Alternative Systems. Might as well do it here. No time like the present, after all.