Hi,
I have Alibre and Mach 3. I use MeshCAM with good results. I am doing this as a hobby, though, and admittedly have not done any 4-axis milling. Please note, you can export Alibre as .stl, which allows direct importation into MeshCAM and others. You can download a freeware version to trial out. It for me has been very nice, and can do two-sided milling operations, place in supports, etc. Good enough for a guy like me. . . Also, don't overlook the built-in macros that come with Mach 3, and also the freeware version of LazyCAM, which can each do really great code very easily! One other thing that you can do with Alibre and LazyCAM is making 2-D art engravings. I use the drawing feature in Alibre just with the sketch tools, then erase the dimensions and export them as .dxf. Then you can import them into LazyCAM and create the G-Code toolpaths for free! If I am outlining a photo, I can import the photo into the Alibre drawing and sketch over it! It is clumsy, but ultimately pretty darn cheap and can do good results.
I am actually looking for an affordable turning package. Med school loans are telling me otherwise. . .
Cheers,
Peter