Also, some people - a minority, but "anecdotally significant" - seem to be a bit smug: like living in San Francisco makes them better somehow.
That said... I don't regret the time I spent there, and it's a city I heartily recommend to Europeans visiting the US, as it'll be a lot more familiar to them than something like Los Angeles, and it has a ton of stuff to do and see. And California in general has probably the most variety of any one US state in terms of geography, so if you get bored of the city, you can go the mountains, or the "lost coast" up north, or Death Valley, or pretty much whatever suits your fancy.