Lots of industrial stuff related to various types of testing. Performance matters some, but I'm not hard real-time.

However, everything has to work, reliably, in less than ideal environments--mostly high-voltage spikes caused by differences in ground potentials.

USB is a PITA because while data is differential, connection detection is not. So, spikes cause USB disconnects and drivers never cope with that.

CAN is a PITA because it is limited to 8-bytes per message. Good for transducers and 8 bit microcontrollers--not so good for complex control and 32-bit microcontrollers.

Ethernet hits a really great sweet spot of fully-differential and nice single packet size for a 32-bit microcontroller--program like it's 1989, baby.

I absolutely agree that Ethernet is ideal and the correct solution for modern systems. Have you worked with EtherCAT at all?