Does this offer any improvement to the way Note Off is handled in the sense Swamptooth meant?

I can't speak to how Sonar handles Note Offs now.  But from that text, it's unclear which type(s) of Note Off messages that the update is referring to.  Note Off: 9nV=0, or Note Off: 8nV=0-127 (variable release velocity).
 

I cant find any software that will let you see it to do anything with it. Strangely many great instruments support it.

The microhosts for z3ta+ / z3ta+2, Dimension Pro, and Rapture (Rapture Pro - unknown) handle release velocity nicely.  Great tools for exploration.  Rapture's microhost can also sync to its own internal tempo.  All of them can record a .wav file internally that can be flown in to another host as a track later on.
 

Sonar wont. Although Insert Piz here have a converter to midi cc

You can do that inside z3ta+ / z3ta+2 modulation matrix using the Function 1-4 routings.  Release Velocity can be used as either a Source or Control modifier (or both).  Functions can split & re-route Destinations to Sources.

Thanks b rock for those pointers
I have been reading your posts since the Project5 days. Many many thanks for sharing your knowledge. 
Ive been trying to archive my increasingly fragile Casio sampler's library of 30 year old floppy discs into sfz format. Without all those tutorials you have posted Ill have no idea how to try and implement the more advanced features like multiple loops
 
It is odd that release velocity is reasonably well supported in older hardware synths but largely ignored in modern DAWs. I have modules from E-mu, Roland, Yamaha and Ensoniq that can use it. 
So far Ive found my Kawai keyboard produce it. I have a few others to try out.
I know that many Roland keyboards will produce it also.
 
Seems to be an area where hardware is still more capable
J