I am using BobCAD and for the most part it is OK. The interface is "quirky", but it does get the job done. They have a MACH3 post, but they also offer posts for free.
I will be getting Sprut - I want 4th and 5th axis support (not offered by BobCAD). I am SURE they have a post, as that is what comes with the Tormach - the same post should work for the Mikini (both run on MACH3). Also, you can get a better price if you buy from Tormach than if you buy from Sprut directly. Tormach offers great support for Sprut as well.
CAD, CAM, Scanning, Modelling, Machining and more. http://www.mcpii.com/3dservices.html