Hello,
Lately I’ve had to prepare some IFC models, so here are my insights about the process.
The model is quite simple, the only problem is connected to its nature: it is a renovation and expansion of an existing building. I could later add some my remarks about this. So, I use lots of external blocks as parts for various VA entities (doors, windows, others), and when modelling with VA it works fine. No, not fine - it works perfectly 
I don’t need the model to be a perfect “Revit” standard, it is just for collaboration with other contractors. Some of them use Revit, some use ArchiCAD, thus an IFC format should be enough. I use their IFC models as inputs for checking collisions and other solutions.
So, first of all I export model using these settings:
Nothing special, except I set off layers with unwanted entities. I use quite a lot of surfaces / curves to model irregular shapes, mostly irregular walls. I don’t want to get a messy IFC model, with lots of proxies, so I just exclude these elements from exporting. Here is a picture with a list of external blocks:
Then, when opening the IFC file with Rhino I get a list of invalid boolean intersection:
Frankly, I cannot say where are these errors, as the model seems to be quite good - except 3 windows:
It is the same style for these incorrect windows. Maybe its definition needs to be improved? I will check it.
When opening the same IFC file with BIM VISION (a free IFC viewer) everything seems to bo good:
A further investigation shows some errors, but (for now) these are not painful (for me, of course). For example, there is invalid assignement of some entities to building floors:
On the other hand, the model keeps original layer structure:
And finally, the IFC keeps user parameters
Here is the model with users’ parameters - as a _Pset category:
And the IFC file keeps these parameters as they should be:
So, I would like to thank you, all Asuni guys, for your hard and good work
Cheers, Jaro
p.s. my structural engineers says he has never get such a good model made with Revit