I'm Canadian, and I joined a year ago. Since then I've been able to join several lobby meetings with politicians and gotten involved in many other local issues that I never would have learned about otherwise. It's quite organized, I get to see the impacts of lobbying, and I meet many other groups that I could choose to join if I am so inclined.
I've found it to be productive. If you feel helpless and are thrashing when it comes to figuring out how to make a difference, I think this is a great first step.