I have only used Mach4 on the wee lathe with the IP-S, mostly worked fine but did have issues with the Step/Dir spindle.
I have an IP-A on the Chiron but I do not feel things are advanced enough yet in both Mach4 and the CS-Lab plugin to risk it, machine is too valuable for me to do that.
If I had a CSMIO controller on the Beaver Mill then I would try it but afraid I only have a USB SS and I do not think there is a Mach4 plugin.
I have seen reports of others using Mach4 on mills with the CSMIO controllers and they seem happy enough but no idea if probing etc is working.
The good thing is you do not have to commit to Mach4 at this stage, both Mach3 and Mach4 will happily co-exist on the same computer, so you can test things in Mach4 and then return to Mach3 for your work if need be.
Hood