The ability to prospect on linked in, create lists and work directly in the program to write customized emails.
Nothing at all. It is simple, straightforward and does a great job letting me do my job - sales.
It minimizes confusion, keeping track of multiple .csv files and allows me to never worry about emailing people twice (unless I want to). I have used Yesware, Vocus.io and Reply.io. They are all great programs but Interseller.io is the best.
Stephen and his team have the most amazing customer service. Anytime I have an issue I hit him up on the chat and they respond within minutes. Really great.