I am not sure what ur service covers, but I would focus on the following:

1. Personally write or use something like http://www1.toutapp.com/ to reach out to the subscribers and see if you can get a 5 min phone call or something. Worst case, send them a survey and provide $5 starbucks card as an incentive. 2. Write content (tips/tricks) email each week and send out

For some people (including myself) I want to play with new tools. For others, it might be a pricing/feature/who knows - which is why you should talk to them