Actually this is one of my Holy Grail Plugs. I don't think there's a vocal track I don't use it on.
I always record about 4 takes for each vocal and then chop them up to get the final one.
I don't always have the best posture and or distance from the mic and many of these takes are at different levels and sonic quality.
I use the 25 db reduction preset.
The Vox plug makes the cobbled take always sound like it was one seamless recording. I haven't been able to duplicate this with any other plugs.
It also works with any tracks that are uneven in volume.
I also use it to boost a quiet track rather than adjust the gain.
The plug also seems to have a small CPU footprint. If I don't bounce harmonies down to stereo I just drop a Vox Ren plug on each vocal channel.
It comes in mono and stereo when you purchase it.
I, personally, could not record without this plug.
Other than that I don't own any Waves stuff.