A few months back, I was applying for developer positions in northern California. Most of my professional experience is in .net, but I applied for all kinds of work, including a rails position. I'm not sure what the average dev/total ratio was for all those, but it's roughly 1/3 where I ended up, with a total size of less than 50. Github was never mentioned during any of my interviews, except occasionally by me to say that I have an account. (though I haven't done much with it) No one seemed particularly interested.
I've had my Github account on my resume for a while now, and the last time I had an interview, they literally pulled it up while I was there and made some comments about it. It didn't seem like a huge factor in their decision, though.
