The beta version of V-ray for Revit is just launched by Chaos Group.
The Chaos Group recently declared the availability of V-ray for Revit beta. By watching this Revit youtube video, one can gather information on this new release of V-ray for Revit and instruction for download. Now it is possible to apply v-ray core rendering technique in Revit for each phase of design progression.
As V-ray for Revit is still in beta testing phase, the renderer is still unreliable and some features are missing. It is suggested not to use it for production purpose. One can export the model to 3ds Max and render there, in the V-Ray Max.
Go through the following link, to register as a beta tester of V-ray for Revit www.chaosgroup.com