Dont think there is such a thing as CAM program of choice, just depends what you have or what you can afford. Lots of people use LazyCAM that comes with Mach, some use the wizards only, some use the addons conversational that Brian sells. Suppose it just depends on what you do on your mill whether you require a top of the range 3D CAM package or can do all you want hand coding.
MasterCAM will I would think work fine with Mach as long as the post processor you use is compatible, might even be one to download if you look about the forum or in the Yahoo group.
Hood