I liked everything about it - from their customer support, easy setup process, ability to create multiple versions of my applications in one dashboard! There was nothing that i disliked at first sight.
We used this tool for managing our application version releases using Git branch system which helped us release new features/changes very easily without any stress or worries :) As we are an ecommerce platform provider so releasing new products /features etc were always difficult as there might be too many changes happening simultaneously (especially during Christmas). Using configcat has made things much easier now by creating separate branches for each product (including beta) and then merging them when ready to deploy :).