Perhaps an apology is in order Alex? Please do not call people names in the future. 
 
"John please lay off the usual attack dog here.... I am not contradicting Noel here, I'm actually reading what he is saying."
 

And when was the last time you ever gave one of those John?

I suggest you stop winding people up and fry your fish elsewhere... Have a good day.

If I read this right, I no longer have to scan at all?  e.g. if I add a VST Sonar will now automatically add it?
My system is now defaulted to a scan every time I start Sonar, but not an issue.
 

SONAR still relies on a VST inventory maintained in the registry by the VST scanner. The default setting for the scanner is "Automatic Background Scan." After adding new VST2/3 plug-ins until scanner is run, the plug-ins will not be seen by SONAR.

The way I read Noel's comments is that a RESET should no longer be required. 
 
Scanning is still necessary to keep the inventory correct/current.

Right, as long as you have the default auto scan settings enabled it should not be necessary to manually scan. 
SONAR detects new plugins added and should automatically scan them. Now in addition, on each launch (for plugins which support it) it will auto check for licences and update itself if new plugins are detected or removed. 

I have a question about the scanner: it now seems to be doing a full scan at startup, even though I haven't changed settings. Or at least, I now see it whizz through all the names of the plug ins in the toast pop up thingy, which I don't recall it doing before. Has this behaviour changed?

That's the way I've always seen it.  I have Sonar set to scan on startup

I have it set to "Automatic Background Scan", which hasn't behaved that way before.

Make sure you have  the default scan options set (rescan failed and rescan existing OFF).
In default auto scan mode it should only really load plugins that have changed or those that require checking for auth.
Do you have waves plugins? Check which names are being displayed.