Recommendations start getting generated immediately after you rate a beer. The site is in its infancy, of course, so recommendations may start out rocky but they'll get better as more people (and you) rate more beers. The sad state of the cold start!

How long it takes for the recommendations to refresh is tougher to say, but it shouldn't be more than a few minutes. I can see that the workers that process them are active, so I'm fairly sure it's working.