We upgraded from ERP8 to 9.0 and upgraded Vertex from 3.1 to 3.4. We changed from a Windows / MSSQL platform to OEL / Oracle platform as well. It was a touch tricky to get Vertex installed on the Linux side, but once installed, no issues. We also use the API for an in-house application as well with no issues using TDM. We did not bring our TDM over from 3.1. Just did a fresh install and had our CFO redo the TDM by hand. I believe there is a way to upgrade and convert Vertex data.