I run a Tormach machine so I am spoilled rotten having PathPilot as a controller. I have just picked up another small CNC on EBay and it came with Mach3 which hasn't set me on fire.
I have therefore been round the same loop on finding an alternative.
I understand that Mach3 is over 10 years old and is not seeing any new work on it. In some ways the HMI looks prototype in many areas. Mach4 is slightly better but you don't seem to be able to demo it on a real machine without paying the licence fee. The Mach3/4 website suggests that it will not run on anything but 32 bit machines but users have had success on Win10. It can run on a Centronics interface or on USB dependent on machine or controller. There are lots of MachX related mods and tweaks videos on YouTube which are helpful but all seem to me to be sticking plaster on basic shortcomings.
So I did a lot of hours on YouTube to see if there was an alternative and found Alan Hollerbach and also martyscncgarage both whom had a lot of experience on Acorn and this convinced me there was perhaps life after MachX.
Last week I attended IMTS2018 in Chicago and found Centroid's booth and spent a lot of time talking to them. They manufacture full blown controllers for large CNC machines and the Acorn is their OEM offering to the smaller shop. The Acorn is a fully integrated dedicated controller for 4 axis and with the Pro version of software is all a small shop needs. It runs on Win10 and on a network connection and has touch control capability. Their website has numerous support videos and there is an active user forum + other independent YouTubers such as those mentioned above. There are larger OEM offerings for more axis machines. Fusion 360 has a Centroid compatible driver script (big plus for me).
I went back on the booth the following day and to my surprise they had shipped me an Acorn overnight to bring home with me. The board is well made and the documents available suggest that it should be relatively stress free to get it running.
Time will tell but so far I am impressed.
(Usual disclaimers)