I rode year round in CA for several years so, naturally, I regard myself as an expert on this matter...
In many cases, lane splitting is much safer than sitting, in line, in stop and go traffic. There's much less chance of being rear ended or having someone cut over into the open spot that you happen to be inhabiting. When cruising a little faster than traffic (at lower speeds), each time the motorcyclist moves up a position, they can time the move with other cars so that there's usually not an opportunity for a car to cut them off. When there is, there's also room for the bike to move w/ the car.
I've always thought that quiet bikes were more safe since cars move much less erratically when they don't know you're coming up behind them. :P It's always fun when a car notices you coming and moves over only to give someone else the pinch on the other side.
Regarding moving up three cars at an intersection... this is a pain if the rider stalls their bike and make everyone wait, but otherwise, its another safety thing. It's a lot less dangerous for a bike out in front of a pack of cars than it is riding in a big clump of cars. Out front, there are always multiple escape paths if a car does something wild.
I've heard the story about CHP being the reason why it's legal in CA. Those guys are like Samurai on two wheels, the way they can move through traffic and keep ahead of the game. I have so much respect for them.