I like that it's easy to use, has great customer support (even during non-business hours), and offers many features for free! The price tag can be prohibitively expensive if you don't need all of its capabilities; however, there are options available at lower prices with fewer bells & whistles than what they offer in their premium plans. We're using them as an API gateway between our app backend services and several other systems we have outbound connections from - such integrations were previously very difficult or impossible without significant custom development work required by us.