I use Manit for my business's manufacturing needs as well processing incoming orders in real time with our customers shipping companies via an API integration into their system of choice (FedEx or USPS).
The tool has been very reliable when it comes down to using its features such that we can process thousands upon millions worth shipments daily without any issues at all! It does take some getting used too but once you do get familiarized then everything becomes easy peasy lemon squeezy :) Nothing really though - just keep up w/the training if your not already doing so because there are many things new users will find confusing initially until they figure out how certain options work together & what each button means etc..