I've used... heck, I use ViaCad quite often to toss together very quick 3d models and representations of ideas the company tosses about. I use the windows version, but I believe that both work essentially the same.
I think it is one of the easiest programs to draw in both 2d and 3d. I do spend a little more time in a different program for strictly 2d work only because the company has a history of drawings with it. In any event, I doubt you will find an easier program to draw either 2d or 3d stuff in.
The history of the developer reveals that it was his ingenious techniques that we saw licensed in some of the bigger dogs years ago, and those awesome methods exist today in ViaCads products. One big cad dog was Ashlar. They used some of the most radical time savers when it came to drawing already 20 years ago. It was ViaCads technology, and frankly, its just in the last year or two that you see others being able to jump on board with some of the methods.
I have used its export tools to send off IGS and STL files from it without any trouble as well as most of the import filters. I do believe that people are having trouble with some of the "automatic" convert solid 3d file to 2d drawings, but I have never even tried to use that option.
The program can really run quick when you learn its few quirks, the biggest of which in my mind is the toolbars/tool buttons/docking methods. They are a bit clunky for todays date, but not a deal breaker.
Beyond that, its a program worth way, WAY more than the $99 is see it selling for..... At that price, it is a steal for what it does. Just order it up... they will send it to you. I have probably purchased 4-5 copies over the years.