Having just gotten back to the UK after my first trip to SF I can see why people like it - it's got a great buzz, and the culture is varied and attractive.

My biggest concern - though it might just be because I was downtown, or that I've not spent much time in US cities - was the large number of homeless. Maybe the Googles and SalesForces in the area could help those guys out?

I love the food and the the fact that the Bay Area has a high concentration of brilliant minds in a very small area. Attending Meetups and talks from some of the leading thinkers in technology has been something that isn't as accessible elsewhere.

edit: Rent prices are crazy though.