I think it really depends on your niche, your social media presence etc.
I am promoting my widget on one of my sites (topadmin.net) and it starts driving some traffic. I also linked to some of my articles on Facebook, Twitter and G+. My social media results haven't been to satisfactory, but in the end some of my articles here might not be interesting to my followers (again, it depends on the niche).
I am planning on adding my hubpages widget on my other sites (I have at least 10 more that could link to it and it should help out more. My main efforts though are to also promote within this site, by being active in the forums/questions section and commenting on related hubs I get "qualified" traffic from this site and the chance to also chat with like minded people.