I have been living in the Bay Area for a few years. The upsides are excellent universities, density of smart people, great weather, and some of the highest salaries on the planet. By the way, California alone is roughly 25% of the US GDP.
That being said, it has serious problems. You need to make a lot of money to live a normal life there, which also applies to a lesser extent to LA and San Diego. The home prices are astronomically high and while they could go higher, I think that buying one would be a huge gamble. As it stands, not many normal people can afford to spend $1.4million for an average house. It IS a great place to be a high earner, as you can make so much more than other cities that it makes the astronomical costs worth it. If you have an average or below average income, this is not the case.
California's government seems to be doing everything in its power to drive away businesses and those with options by making higher taxes and business-unfriendly policies. On the flipside, Cali is the home to Silicon Valley and Hollywood. While they might do better relocating elsewhere, it's unlikely that will happen immediately, or ever.
On a personal level, I think it is currently a good place to be but it is crumbling. I absolutely would not invest in California property aside from maybe a personal residence. In the bay area, you are lucky if you can break even from rents, most likely you will be underwater hoping that property values and rents appreciate enough for you to make a profit. Seeing as the prices are already at the point where people can barely afford them, that's not a bet I'd be willing to make.
One interesting metric you should look at is the price to move TO California vs the price to move FROM California. A few months back, a regular u-haul from the bay area to Oregon cost about $1200. The reverse was about $250. When I asked about the huge price disparity, they said it was due to supply and demand. That sounds like a ticking time bomb if I ever heard one.