The ease in which you can integrate your system into theirs without having any technical knowledge or experience! They will work through all aspects for ensuring everything goes smoothly throughout this process from start till finish as they have done so many times before me personally at other vendors we've worked together over time (ie., UPS).
Nothing really I dislike about them but maybe could be that sometimes there's some lag between when something was posted/received by us versus what it says here within orderfull itself - however small amount might not even matter though? Not sure how much control i would like if such things were my decision vs those above who are "making" decisions etc.. But overall great product easy integration and excellent customer service team too!! Highly recommend getting onboarded via live chat / video call rather than emailing back forth because communication takes longer then expected during initial set up phase especially since one party doesn't know exactly where another stands along timeline until both.