> I am currently trying to get FreeDyn, a multibody dynamics simulation program to work with it [1]. I have used the FEM workbench to do simple FEAs too. It's an amazingly open platform with a lot of potential.

That would be really cool! I know there is a lot of interest in e.g. a kinematics workbench.

How do you handle assemblies efficiently? I found the assembly workbench to be a major weakness of FreeCad when compared to Solidworks or Inventor.

Typically I am not working on assemblies of more than 10 to 20 parts. You're right though, Inventor and Solidworks do handle them better, but with a lot of complexity that scales better when you are working on assemblies and subassemblies of over 100 parts or more. I used to work on machinery with more parts, but now I work on sub assemblies with fewer parts. The assembly workbench will improve when people who have a need for it improve it in FreeCAD. I used to do assemblies with CSG over 15 years ago, and it was complicated, but I was very frustrated in the early days of Inventor when you went down a path, and then found yourself painted in a corner by the history or constraint tree. Changing one thing, and watching it all blow up was my first letdown after jumping on the parametric/history modeling bandwagon (I also used SolidWorks and IDEAS). FreeCAD has come a long way, and I use it more often than before. Quick startup times and fast working with a great Python API (I used to program AutoLISP for comparison).