The ability to create custom audience segments that are then available as targeting criteria through our agency clients is one thing I like most about this product! You cannot import any other kind of list aside from email lists. We have created many different segmentations using demographic data points we were able to obtain directly from Facebook profiles or even phone numbers entered into our contact record management system. This allows us to use those same audiences with our client's campaigns. It also gives us full control over how much traffic each campaign receives versus others. There isn't anything really negative here at all; it did exactly what was promised. The ability to reach out to our customers and make them feel like they are part of the team. It really helps with retention and customer service. There is nothing that I dislike about this product. If you want to engage your customers and have a positive experience, then this is the way to go! We are able to target specific people who are interested in what we do and can give them more information on how they can help them with their business.