And if so could you explain it's VST3 limitations within Sonar to me??  Does it ride the vocal or not?

Yes, it rides the vocal, helping to keep it level.  It automatically corrects for fluctuations in input volume.  What it can't do in Sonar is ride the vocal based on what other tracks are doing.  It uses VST3 for its sidechain function, and since Sonar doesn't do VST3, it no worky for that.  But it's still very useful and saves lots of manual effort.  If you haven't got it, it's a no-brainer at the current price with voucher, IMHO.
 
Cheers,
Eddie
 

I had it and sold it.  It will ride the vocal level without VST3, but it's essentially just using a preset target level range (basically, it is automatically riding the level).  With VST3/sidechain, you can route a music track/bus into the sidechain and, therefore, ride the vocal with your music as the reference level. 

Hmmm.  thanks to both of you fellers.  I'm gonna ponder on it.

I would not mind mentioning some techniques that I use for vocal riding. Firstly I do it manually and the reality is that a human doing it is way better than any VST doing it.
 
I have been tracking vocals recently for a female pop singer. She does have some phrasing that is a little louder and some bits that are a little quieter. I have been riding the gain on the way in to the DAW. Yes it is a bit dangerous for sure but the key is to really learn the vocal line all the way through before you even attempt it.
 
In Studio One the whole takes and lanes thing is really excellent and it all works of course but you can also see previous takes under the one you are currently recording. The waveform height of the takes without any riding on them can give a clue as to what is coming up etc and you can easily pre-empt things about to happen like a loud section. The trick too is to use a fader (rather than a rotary Mic Pre knob) and not make wild changes either a few dB here and there.
 
When you get a real nice manual vocal ride I then edit the vocals a bit more inside an editing program for just some final touches. After doing that you will end up with a very nice even vocal track that requires very little dynamics processing in your mix. As a result it will just sound better and nicer. The softer sections of the vocals end up being real clear and all the diction is present too. You cannot beat a great manual vocal ride.
 
BTW the ultimate way to do it is to keep the singer perfectly still and you put the vocal mike on a movable boom and you move the mic in and out towards the singer etc according to the vocal lines. This is harder and some singers may even want to get you arrested for doing this as it looks pretty strange but it is the ultimate vocal ride ever. The trick is to learn just how far to pull the mic back for the louder bits. It is the finest vocal compressor ever! But the next best thing is a fader vocal ride.
 
Anyway looks like the Waves is only really useable in VST 3 mode.

I got it a couple of weeks ago and love it.  It's the first thing in my vocal FX change, generally followed by Izotope's Nectar.  I've been satisfied with the default range so far, but you CAN modify the volume range.
 
As far as using a sidechain/ducking FX, I've been liking the new version 2 Trackspacer.

I tend to use it before compression to minimise the impact of compression on louder parts ..
 
great plugin Pal

Thanks Zo, ol pal.  I picked it up.  I'm such a gear slut;-)
 
And the price was soooo good.
 

 I bought Bass rider and was then tempted to follow up with vocal rider. I guess I'm kicking it around too. Since I sometimes track myself it can be difficult to work the faders while singing.