Easy configuration of business logic using XML schemas is my favorite feature that I have used so far! The support team has been very responsive as well when needed during implementation phase or after go live date - they always provide quick resolution by either contacting them directly via chat/phone call if it's urgent; otherwise we will be notified through ticketing system within few hours upon escalation from our account manager who was assigned this task initially (if required).
Very flexible & easy way to configure SOAP messages without writing code yourself which makes life easier while working remotely at client site.