We have used this plugin on a productive site for more than a year. Unfortunately, it has bugs in important places, which the friendly support is willing to correct only against paid customization, which starts at several 100 dollars. Moreover, despite comprehensible and detailed error messages, the support refuses to build its own environment to reproduce and fix the bug and insists on unrestricted admin access to the customer's installation, even if it already contains live sensitive data. They insisted in this and have not shown one bit of willingness to compromise. Therefore obvious bugs were not fixed from them.
The shipping settings on the merchant side is a cumbersome and incomplete. This is solved way better in other plugins.
Also in terms of feature set, this plugin is not geared towards the more tightly regulated European market.
We finally had to switch to another multi-vendor plugin after all the bad experience.