Anyone have advise on installing both VST2 and VST3 versions?  I just acquired Cubase and so suddenly there is a reason to consider using the VST3 versions.  But obviously they won't work with SONAR.  Can I have it both ways, or should I stick with VST2-only to maintain compatibility across the board?

Yes, you can have all the formats on your PC. You are not going to mix plug-in formats in the same directory. I can't imagine why you would not use the VST3 versions in host that support it. It is not like you can move projects between hosts at the plug-in level.

VST3's don't get installed into your VST2 folder if that's what you're after.
 

carl
VST3's don't get installed into your VST2 folder if that's what you're after.

Here's what I have (based on suggestions made by others in this forum) and it has worked very well so far.  I let the Cakewalk plugs get installed to the default location the installer chooses.  For third party stuff, I have C:/Program Files/vstplugins/vendor where vendor is FabFilter, NomadFactory, etc. and I have a similar set of directories under Program Files (X86), not that I use anything there these days.
 
So, should I now create and use: C:/Program Files/vst3plugins/FabFilter to place the VST3s?  This seems like the most sensible course of action, but I'm not sure if that's what others who have already done this would recommend.

Just let the installer do it's thing. You'll find them IIRC here-
C:\Program Files (x86)\Common Files\VST3\

FabFilter releases minor bug-fix updates

We have just released minor bug-fix updates for all plug-ins, which solve a couple of small issues that have surfaced after the last update release in June.
 
We have just released minor bug-fix updates for all plug-ins, which solve a couple of small issues that have surfaced after the last update release in June.

• Fixed a bug that could cause typed parameter values to be rounded incorrectly, e.g. when double-clicking to enter a frequency value in FabFilter Pro-Q.
• Fixed a bug in all AAX plug-ins: after deactivating a bypassed plug-in in Pro Tools, the state of the bypass parameter would not be restored correctly on reactivation.
• Fixed a bug in the AAX version of FabFilter Twin 2 that caused the external side chain input not to work in Pro Tools.

http://www.fabfilter.com/download