FreeCAD supports fillets, if your order of operations is set up the fillet will be applied to your features after and it will update the fillet with the changed dimensions, like a parametric cad system should do.
1) Open CASCDE geometry kernel, this is the heart of the cad system, for example Solidworks uses the Parasolid geometry kernel; which is owned by Siemens.
2. A powerful data structure; the feature tree that FreeCAD has is object oriented, and capable of adapting to complex tasks.
3. GUI written in QT, with a Python interface to instantiate the GUI. This allows you to load FreeCAD while in Blender and vice versa load Blender from within FreeCAD; this facilitate the sharing of geometry data, meshes, the OpenGL geometry pipeline, etc.
4. Support for Jupyter notebooks, this is important when you are doing analysis or something complicated and you wish to share and publish that data. Using SciPy , NumPy, and Octave its like running Matlab + CAD, its so powerful that you can drive simulations this way directly effecting the FreeCAD GUI.
5. BREP Internal data structure, in fact when you save a .fcad file extension, that is essentially a BREP file format, which is essentially a STEP file(a type of BREP). This is essentially what the professional CAD packages do, they are BREP with custom data structures.
6. BREP + STEP allows for extremely precise importing of model geometry. This allows you to download parts from McMaster, Berg, Pic Design, SDP, etc and use them in your design and generate a BOM from the precise part bing inserted.
7. Support for different mesh tessellation methods, this is important since working with manifold topology that is held internally by Open CASCADE or STEP can be non trivial mathematically to interpret.
8. Runs on Linux, OS X, and Windows natively.
9. Open source, so you are in control of your own destiny.
While FreeCAD has some rough spots around its edges currently, where it will he in the future if we invest our collective brainpower and knowhow into will far surpass any offering from Autodesk, Solidworks, as the rate of evolution of OpenSource compared to closed for profit systems is much more limited. We can as a community experiment with edgy things and push into new frontiers with our creativity and imagination and disrupt an entire paradigm the CAD industry uses today.
Blender already has advanced support of GPU real time ray tracing supported on the most recent GPU offerings, and is able to harness massively parallel compute for rendering and ray tracing. We can harness those same capabilities for an open source CAD platform, and use the GPU compute for the FEA capabilities.
In the part design workbench you can create a sketch, you draw a rectangle and you can extrude your box to its precise dimensions with a precise wall thickness.
Then you can create a sketch with your features on the surfaces of the part, the sketch features such as holes(circles) connector cut outs can be placed based on a dimensional constraint. Extrude and cut your features.
Now you have a 3D box with your holes where you placed them; now need to move a hole change the size of the hole, its as simple as editing the dimension the hole is defined in the sketch, all the other features will update as needed, and you can layer the dependencies forming a feature tree dependency graph.
Should take about 10 min to create a pretty complex case enclosure.