Antimony – A fresh look at CAD software
Okay, I'm a CAD software developer instead of an actual CAD engineer, so my perspective may be a bit biased.  But this CSG (constructive solid geometry) idea is not in any way new.  The reason it's kind of obscure now is that spline-based boundary representation systems (B-reps) took over the market decades ago.  If you think about, say, the latest car designs, those free-flowing shapes are pretty easy to do in B-rep, and quite hard in CSG. [1]I've worked in CAD translators for the last two decades.  Though both the IGES and STEP file formats include CSG modeling features, I have never implemented them.  To the best of my recollection, I've never even had a request from a customer to do so.  A pity, I think they'd be fun to try to implement... and most of the thorny bugs would officially be the B-rep geometry kernel's, not mine.  :)[1] http://en.wikipedia.org/wiki/Boundary_representation