I played around with BRL-CAD about 2/3 years ago. A very complicated design interface (everything was command line input) and drawing something as simple as a die (cube with fillets) was quite a lot of work. On top of that it is not parametric which makes it impractical for day-to-day design use on a professional level. Add to that tthe fact that it could export as iges, step, etc.

I'll try it again, but just for the fun of it. For the youngsters in the CAD community it would be great to learn it as it will teach them A LOT about the early developement of CAD programs.