As a resident of SF I find coffee-shop laptop users to be a pest in busy cafes. Coffee shops are a great social environment, and dominating a seat for an extended period of time while you are immersed in your computer runs counter to that culture.
The other side of this, however, is that if I need to work somewhere and I don't have an office, where can I go? 2 people cannot comfortably work in my dinky condo (I can barely live in it...) and I don't want to pay $100+ for a co-working space. Compared to a $2.50 coffee, that's insane!
University libraries can also be good, but be mindful of the date. If it's exam season I tend to avoid them simply because students should have priority to the libraries they are paying for.
I'd like to see someone open a cafe that has a communal-only seating policy, perhaps even you are assigned to a seat in one of the communal seating areas, no laptops. The cafe promotes active engagement and conversation amongst people who do not know each other. A return to the original purpose of the London coffee house -- a place to debate[1].
There are plenty of coffee shops where people are buried into their laptops already, but as this article demonstrates, some people really do want to talk to people they don't know, but they find it tough to get out of their comfort zone. If there's a space where this is encouraged and promoted, I think many would welcome it.
[1] http://www.telegraph.co.uk/travel/destinations/europe/united...
And no, I won't tell Hacker News where it is. ;)