I believe the law in CA is that it is legal, but the motorcycle rider must not split lanes at a speed faster than 15 mph above the flow of traffic. I did it a few times when I lived in Los Angeles, but mostly just went to the head of the line at every light. In a city like LA, that cuts your traffic time by 50-75% minimum! And honestly, at least where I was riding, traffic often never got above 45 mph because it was so congested, so it didn't seem particularly dangerous riding around that town. People were surprisingly good drivers and I never experienced any anti-motorcyclist anger, but I ride like a wimp (according to some macho friends!) and just enjoy cruising without going too fast. Of course, I was also still hyper vigilant and assumed that no matter where I was, I was invisible to all cars on the road! Safety first for me. I once saw a guy get clipped merging into oncoming traffic at what was probably 60+ mph right in front of me, and I will never forget how awful that was...