I live in the mission. It's amazing to be able to walk between a dozen coffee shops and bike to work. But it's not for everyone, it's especially not for people who don't want to sell one of their organs each month to pay the rent.
PG extols the virtues of Silicon Valley, which is basically coincident with the South Bay. He actively dissuades (unsuccessfully, in many cases) YC founders from living in SF.
Personally, I think that's where it belongs and that having "everything" be "so nearby" in a city is both a fiction and overstated as a benefit.