Traffic from Google can be very slow at first. If you are getting a few visitors from Google in the first few weeks after publishing a hub, that is a good sign. In my experience, it takes anywhere from a month to 6 months for organic traffic to pick up from google, and that's assuming the hubs are properly set up to do well (keywords, SEO, good content, etc.).
I have had hubs that picked up traffic very rapidly, but they were current topics and have since trailed off.