It's best known and used for its mass mailing and signup pages. Those are the primary uses for it nowadays.
It's pretty user-friendly and can accomplish most desired tasks for new users and power users. A lot of the most important features are built-in and easy to find. It can handle the most robust code/data of this tier of political CRMs.
It's reporting functions are limited, and the product is rarely if ever updated/upgraded. It was best in class for a while, but Action Kit has certainly passed it at this point. It can be buggy, and servers are shared so other orgs can impact your deliverability and when it tanks on deliverability, it is often across the board.
Understand the scope of your project and needs before signing up, but if you are looking for a mass mailing program, then this is your best option unless you can afford Action Kit.
Email list management and sending. It's the easiest for people with limited code experience to understand/use quickly.