Hi I am not the devinitive sorce on all that is mach 3+ plug in but i am running it and can give a couple of answers.
Probing, no
home, limits, yes
jog, yes
it will do everything that mach 4 will do. and seems to be more stable. As far as i have heard mach 4 is not fgoing to get any more code work, everything is going to be mach3 and the g100 plug in
Chad