you can use M3 to do 500 lines of code for testing you can use the ESS with M3 or M4 I, do pendant stuff is coming if your pendant is a key sniffer type you can use those in M4 there's a keyboard plug what was done for test reasons that will work with key sniffer type`s.
from the next relise I will only be using M4 as long as the ESS plug does not get broken if I have any problems I still have M3 to use.
if I could I would try the uccnc to see what`s better, I have tried the new version of linuxcnc don't like it one bit.
the main reason I am staying with M4 is I can run a Laser and a router on the same machine and what hard wear I have now works with it, pendant plug is next month sometime hopefully it use`s the same langue as my cad it just does what I wont and it`s not quite finished yet.
so badwolf stick with the uccnc for now I will give you a update when I do some cutting next week if you wont, I think uccnc is going to do a plug for M4 as well dubble can you answer that question please