The converter is top, works without problem for me (ok,...I have a qualm with that 999IOR being default instead of 1.6, but that's about it) in almost all cases.
I don't want to go too offtopic here but this is actually a feature (or should be if it's not a bug..). The script sets ior to 999 if the fresnel checkbox in the converted vrayMtl was switched off - so it's switching it off in Corona too (which is ior of 999 according to Ondra).
If it happens in other cases it's a bug and should be reported ;)
