Should i buy the mach 3  now or wait for 4?

What is actually the difference?

It says that 3 will be discontinued?

My conversion is almost finished.

Thanks, john

Mach4 is a completely new control, written from the ground up. The biggest issue is that I don't think anyone really knows how close it  to being "finished".

Are you using a parallel port, or motion controller? There are very few Mach4 motion controller plugins available right now.

I'm using the Ethernet smooth stepper for my controller.

There currently is no Mach4 plugin available for the ESS.

If you want to use your machine right away, Mach3 is probably your best option right now.