If antialiasing is needed for a scene, setting Output type to Color (with AA) gives the best results.
Setting the Output type to Integer (no AA) renders slightly faster, although with no antialiasing.
The name of the Object ID render element must consist of the name of the Object ID itself, a dot and then any other string to be properly read in Nuke. For example, VRayObjectID.example . Do not include numbers in the name.