so far, i have had full success with models only (no animations):
Converted successfully and materials made successfully
Not successful with meshes or materials
- ms3d: Smoothing group issues, but materials work
- lxo: No materials
- x: smoothing group issues and came in 180 degrees on the Y Axis, but materials work
I have only tested one model so far in the different formats it has, other models may work better than others.
My best choice for a format so far is .dae.
Assimp does not seem to have a .fbx import, strange, ill look into another way of getting support for FBX Models

Heres a quick image:
