The main impressions I got were:

• Berkeley is appealing (to me) near the university - it has a nice cafe+bookstore vibe. The rest of the city is too spread out and potentially dangerous (a bus driver I talked to said his bus had been shot twice).
• The BART works pretty well, if your destination is near a station. The bus system in San Fran proper is not so good.
• I didn't like the parts of Oakland I visited.
• A studio apartment near the downtown Berkeley BART station is about $2k/month.

As an exercise, I broke down three cities (Boston, San Fran, Seattle) in terms of various dimensions (weather, social environment, business environment, cost of living, etc) and put a yearly dollar amount on each dimension, representing the value relative to Boston I'd be will to pay for having access to it. I was hoping that I would observe something like a $10k/year effective boost from moving to San Fran or Seattle, which would indicate a strong benefit to moving. I found only a $1k/year boost. I gave San Fran a $15k/year benefit for having better weather, but most of that was eaten up by a $10k/year increase in cost of living. The rest of the dimensions seemed pretty comparable.