I have done some tests with this exporter since I do the majority of my development work in Unity these days.
The results are dismal at best, at worst totally broken. I have a list as long as your arm outlining the problems you can expect to see, but as a sample look towards HIfi’s own description of the results.
I tried this a year ago and have no idea what the results might be with Hifi’s current release.
Since there has been no movement on this project for nearly a year I would expect unresolvable problems using the newest Unity releases, if you must do this thing then stick with the old Unity version.
Look at the list of known limitations, that will tell you whats not going to happen.
ie. Particles and scripts are ignored.
Parents which skew their children will not import correctly.
FBX format will only recognize diffuse maps and normal maps when exporting, the non support of specularity and hardness maps is a problem in terms of good rendering finish.
Some of the issues I encountered:
Textures are completely wrong, Unity primitives which are textured in Unity are all messed up including colors, mixed up textures and incorrect mapping, but mesh objects built and textured externally and imported into Unity are in better shape but still have problems, shader order seems to be reversed so the spec maps become the albedo etc. UV mapping remains intact. Although some objects arrived completely blank. Invisible game objects arrived as white primitives.
In short with the current state of this importer I am tempted to suggest it would be more work to import an existing complex project and then try to fix it, and it will still not look or behave anything like the original and it will probably be better to rebuild the project entirely in High Fidelity.