I like to flow of the process, when I log in I immediately see my orders, do my download and I am ready to start shipping.
The set up process with connecting orders is as always a little confusing, but the support is great, and once the set up is complete then the hard part is over. other then that there isn't anything negative that comes to mind.
I signed up to use it for my shipping, printing packing slips and postage, and it works excellent for that.
I now also use it for all my customer service, great easy system with a folder for CSR where I can send the orders they need to deal with, or make a note and send it to them. When my csr logs in it is all on her folder.
It is also populating my Mail chimp account with my customers emails so my marketing list is always up to date.
And lately we started using Taxjar for help with tracking the sales tax, and OM is integrated with them too.