I think the world has changed drastically in the past few years...
I can provide perspective from working for a startup in SF in 06-07 and a startup in Chicago now... In Chicago noone thinks you're unemployed if you say you work for a startup. That was the case a couple of years ago, but with Groupon and a TON of other companies that just isn't the case. The difference is just that more people are doing startups in SF vs. consultants/bankers/fortune 500 workers... Go to a bar here and girls think it's so damn cool that you are running a startup (apparently girls are obsessed with all things geek - http://www.chicagobusiness.com/article/20110924/ISSUE03/3092...).
Re: the coffeshop thing- just by chance (ie we didn't know this going in and it is NOT the startup hub area within Chicago), within 3 blocks of FeeFighters office are: 37signals, SproutSocial, Threadless, Crowdspring, and several other startups. I don't see how it helps us significantly to bump into them (though we have helped our neighbors when they've had merchant account issues). Many people think it is a wasteland anywhere not the valley but I have seen that not to be the case here, in New York, and even in Pittsburgh.
So what is the difference between here and there? The largest differentiator I've noticed between the valley and elsewhere is funding. We raised most of our money in Chicago from VC's we really like, but could have raised easier on the west coast. A lot of top VC's prefer to have you close and told us flat out they would fund us if we moved there. We had term sheets dependent on us being in Austin, SF, and LA. I don't think it has had an effect one way or another on our business thus far.
Startups need money, and often flock to where it is. Things are changing all over the place though (Rich people in Chicago all of a sudden want to fund startups, will be interesting to see if that continues post-Groupon IPO)
It also depends on your type of business. If you sell mainly to startups, you should probably be in the valley.