Best features are - Easy booking of shipments across multiple carriers with just few clicks; best part about it being API enabled which allows you to integrate other systems/apps easily via SDKs or APIs (which makes integration super easy).
No cons as such! They have great customer support team who has been very helpful in resolving issues that we faced while working through their services so far. We were looking out only carrier agnostic service at one place but they can be improved upon by adding more additional shipping networks like USPS & Shipping lines too!! It's not free yet but I am sure this will become better over time once there start charging per shipment booked using them compared to current flat fee structure where charges increase exponentially depending upon amount shipped. Tracking all our containers from loading till delivering right at my fingertips without any hassle was most amazing feature we got after going completely paperless way back then.