I use ABB VFD's to drive the motors in our machines, preference being ACS 850 but also ACS 550. The ABB's have an ethernet adapter module and they use Modbus TCP to communicate.
I also use National Instruments Vision Inspection software (Vision Builder for Application, aka VBAI). It allows communication with other software via Modbus TCP.
They have both been very reliable, and once I adapted the Modbus Integration kit to my needs, configuration has been fairly straightforward. I have been able to use standard ethernet switches to manage communication between the PAC controller and these and/or other ethernet controlled devices (using more customized protocols), along with PAC Display. It makes wiring and troubleshooting communications much easier than it used to be.
The Modbus TCP control of the VFD was a recent experiment, most of the machines use hardwire control. I like it, and intend to use it in future builds.
I would like to build a gas pressure manifold using valves that can be set with Modbus TCP, but haven't spent enough time researching to see if they exist commercially.