Hi John,
Looking good,
In Mach3 if you hit the limit switch it stops the drive and requires you to rest the "REST". After you have done that you can move away from the limit switch (Mach3 keeps you at slow speed till you are off the switch).
Second point is that when you tell Mach3 to Ref Home it moves to the limit switchs and trips them then moves back till they are not on. If you wire the drive to shut you won't be able to set up your RefHome.
I would be honest and say the ability to set the refhome I love, it makes life so much easier to work the machine.
Hope that helps.
Tony