My new mill uses Mach3 with an Ethernet SmoothStepper. I hoped that this would be a reliable combination but I get the occasional hang for no apparent reason, and it can then be a pain to reset and pick up from a specific point in the gcode. Don't know if it's the ESS, Mach3, or the pair of them together. The mill has both a tool touchplate plus touchprobe (a really cheap version but it's OK - and I can make new probes for when I break them...) and to get those both to work with Mach3, it turns out that you need to use an undocumented Mach3 command to switch probe inputs on the fly. Took ages to find that one. Mach3 is getting to be less and less fun these days. I'm using the PV ET6 on my router, although that has its moments as well. I'm probably going to switch to running it on Linux rather than Windows to see if that's a bit better.

So, I'm also wondering about changing controllers on the mill, although it's going to be a bit of a faff as all the probe/motor/limit switch etc sockets are mounted on a single board that also has the ESS plugged in. Quick question, then - does the 300ETH etc plus UCCNC support multiple probe inputs?