Quickness and easy access, and if there is an issue, they fix it in a reasonable time!

AutoKlose is an excellent email-automation tool, that give you the ability to send personalized emails to hundreds of people from a single email. Unlike other services, AutoKlose gives you unlimited campaigns, tracking, follow-ups, and contacts. Have a very friendly and straightforward interface (but ugly colors for my taste) Also comes with analytics and tracking, so you can view who opened your email, who responded, and others stats. It can be overwhelming if you have never used such a tool, but it is very easy if you have previous experience in email marketing. Finally, i love they provide API, and integrations like Zapier.

The reports have one of the best reports, and that we can make them automated is excellent. Also, seeing the metrics from each user that has called on the same project is fantastic!