Some perspective from a current SF resident:
I like SF a lot. That said, it's got some problems. It's a generally pretty good fit for me as a white-collar, socially liberal thirty year-old guy who enjoys stuff like going to rock shows, playing in a competitive adult skeeball league, and drinking more than is probably healthy. I actually enjoy the urban environment and the possibility of getting around relatively easily on public transit. I don't own a car right now, and either walk, take the bus, or our the local commuter rail BART, which I do every day since I work across the SF Bay in Oakland.
As others have suggested, if you and enjoy and are in a position to go out and partake in the local culture, there is certainly plenty of it here. You could do one of many different things every night of the week and still miss a lot. If you prefer to stay home it's probably not worth putting up with the noise, occasional smell, and housing cost. Right now that last one is the biggest problem for a lot of folks. You'll be looking at no less than $2,500/month for a one bedroom apartment in a decent area, and probably more than that. I pay $1,140/month to share a pretty nice Edwardian flat near Alamo Square with three other people. I would not advise trying to buy a home in SF proper. If you want to do that, you'll have to head well into the East Bay to find something you can reasonably afford. In the general the weather is great here, although it's a bit cool in the summer. We're having one of our first "very cold" winter days today and I think its 53 degrees out right now.
The SF Bay Area has a lot going on in general and I think it's a nice place to live. A lot of other people evidently do as well, or it wouldn't be so f*cking expensive to live here.