From someone who lives in in SF area: the weather is freaky (although living here my whole life and visiting other hellholes around this world, I love it more than any other), there is a ton of stuff to do (just like NYC), they have a pretty good music scene, and there is some pretty good live poker around here IMO.
Also, SF can provide ample opportunities for most career paths.
BTW, staying at a job in the Bay Area for longer than a year is a long term commitment. I wouldn't really worry about staying at the job long term in this area. I have very successful friends who are on their tenth or more job, and most everyone I know my age has had about 5 jobs at least while staying an average of 1.5 years at each location. Depressing, but standard in this area.
Another thing: the economy has been taking a sharp downturn in the past month or two, and although I really don't know how that affect the job market around where you are, in the Bay Area they lay people off around here in tight times very quickly. I am not sure what this means for the company you are getting the offer from, but a promising business can disappear really quickly in a bad economy if they lose their VC money.
Hope some of this helped.