I like that this system is easy to use, has many options for customization as well very customer friendly support team! Honestly nothing really but if you are looking at an affordable solution with great features then definitely look into EDA!! The price point makes it hard not only in affordability but also ease of implementation especially when using outside sources such as MailChimp or others which can be costly sometimes depending upon your budget (I am sure they have plans). We needed something inexpensive yet customizable so we could track our campaigns easily without having much technical knowledge required by other systems out there.