I've lived in CA since the seventies. The air quality in the Bay Area has continued to decline over the years. I can remember going up to the Berkeley Hills on a regular basis, about two or three times a week, during the mid to late eighties. At that time you could see SF clearly any day of the week. You could often see as far as San Jose.
Take a trip up to the Berkeley Hills and have a look for yourself. The air quality here is comparable to what is was like in LA in the seventies and eighties. We are not that far behind Mexico City.
The law has been passed. It may be flawed and we may not like it but it's the law. Implementation may be rolled back, just as digital TV was rolled back, but it will be enforced at some point in time.
I'm not thrilled about smog checks. One of the reasons why I purchased diesel vehicles was to avoid smog checks. Smog checks are time consuming and they can be costly. However, the new law is going to benefit my children, for that I am grateful.