What’s the new Vray motion blur setting? As far as I can tell, it’s working already in .04.
It’s for the case where:
- Frost’s meshing mode is set to “Geometry”,
- Frost’s “Use V-Ray Instancing” is enabled,
- Your renderer is set to V-Ray, and
- V-Ray’s Camera -> “Motion Blur” is enabled.
I might be missing something, but I never saw motion blur work in 2.0.4. If motion blur was already working for you, then I’m guessing you might have had Frost’s “Use V-Ray Instancing” disabled?
Definitely am using Vray, 2.0.4 and Vray Instancing checkbox. And definitely getting motion blur. 
EDIT: Oh nevermind I’m not. It’s the camera motion blur only.
Ah! That would explain it, thank you for letting us know!