Well, I managed to find an expired demo of V-ray. I was able to open this scene, took forever though. At first, when this conversion window came up, I chose to update the Vray stuff. The materials just never finished updating as they just appeared transparent (checkerboard, but if I clicked on one the beach ball would come up so it was doing something. The ones that did finish, remained as checkerboards and took a very long time. I closed it out and reopened, but this time, I chose to hit cancel on that Vray screen which seemed to work. I could see the textures in the preview spheres Immediately. Hit convert scene and overall a good job getting me close to where I need to be. This scene is a city street and a handful of items did not convert completely. Anything with the tag below was left untouched. The street material was a complex material and I was only able to get it "in the ballpark", but usable. There were a couple of cars in this scene and none of the glass materials came through correctly. Transparent yes, but like air. Tomorrow, I may go through and see any other specific Vray shaders that didn't convert in case the devs don't have them all on their to-do list.
There are light poles in this scene too and they had fake light glows created with planes, a light glint/haze and a luma matte in the Opacity node. The opacity just didn't work right, even though it seemed to be set up correctly. I played with the exposure of the matte to no avail. Seems like the leaf materials for some trees had similar issues.
LegacyVrayShader did not convert at all. You can't even see what textures were used in them either.
Would be nice if the converter had some sort of progress bar, just for sanity's sake.
P.S. I did not explore the Corona Legacy material vs. converting to Physical if that makes any difference.