Well while the forcing people to do it may not be particularly cool, the fact is, unless you're planning to breed the animal, there's not a lot of reason to not have it done. The majority of pet owners have no plans of ever allowing their animals to mate. And most animal shelters won't let you adopt a pet unless they spay or neuter it first anyway. I know people get a bit uppity when they're faced with the possibility of being forced to do anything, but it's something that most people should be doing, and probably would already be doing. In the end, I think this would mostly only affect the people who are the problem pet owners. Anyone seriously interested in breeding would just file for it like they do any other papers for their pets.
It's not final though, and I have a feeling it won't be. And I don't see it going to any other states unless there's a particularly big animal problem, which most states just don't have compared to CA.