The $20 upgrade gets you ATC and things like being able to file from the FMS route etc. It’s been a while since I used it, but it was pretty neat at the time. I wonder if the plug-in windows would appear in VR. I think I’m going to have to try it again tonight. 
EDIT: From before here’s a sample of what it does: Does anyone use the ATC in X-Plane? - #5 by fearlessfrog