I have been using MACH2/3 for several years. The CNCDIY machines are made to work great with this program (http://www.machsupport.com/) .
When I received my last machine, a sheet was incuded that showed the settings for the MACH3 configuration screen.
Of course you have to know a little to do this kind of thing. But if you weren't smart, you wouldn't be considering buying one of these, would you?
Also, the best CAM software I have found is from Mecsoft.