scook
DXi plug-ins have always been segregated from VST plug-ins in the Cakewalk plug-in menus. One of the reasons given for an extra level in the Cakewalk plug-in menus was to handle very large plug-in counts.

That is a very practical reason for the way plug-ins are segregated in Sonar's plug-in menu. I have customized my plug-in menu into plug-in types, some of which have large number of items, which is a lot cleaner than having all plug-ins lumped together.
 
I've never seen it as a "showroom feature" - Cakewalk had to start somewhere with the menus, and offer some sort of organized menu, and this is what they gave us. But as others have noted, the menus are customize-able so users aren't stuck with the standard view and you can change it to an organization style that works better for and looks better to you. I think that if "showroom" was Cakewalk's point, they wouldn't have offered the customization.

Ruben
 
I've never seen it as a "showroom feature" 
 

Agreed. I can't imagine someone at Guitar Center saying "And best of all, check this out! Separate listings for VST2 and VST3 effects!! Take THAT, Pro Tools!"

Thanks all the various thoughts.
 
Started with CW9, and then Sonar 1- x3.  Since my setup of 8.5.3 is heavily de-cluttered, I cannot refer to the default, out-of-the-box, plugin menus.
 
I use custom folders for ALL plugins, including the Sonar stuff. So I have had to modify the plugin layout, with each version of Sonar.
 
I was trying to figger if I should be doing something different.
 
The X3 plug menu seems more of a "decluttering" issue by adding one more menu segregation requiring users to pay more attention to the interface.  (A general sadness for me.)
 
I can understand the need to make sure new projects use the latest plugs, while keeping older plugs available, but not easily mistaken for the newer bits.
 
I still use many DirectX plugs. Including the "old" CW amp sim (Lots of hard harmonics).
 
Is it Reaper that identifies the type of plug as part of the plugin name? Seems a more reasonable approach than the user having to be sure to add plugins into specific folders, and then modify the menus,..... And it provides for quick sorting and filtering.
 
"Showroom Feature:" 
  Working at various audio equipment stores during the 80's we often lamented the baked on product descriptions (4 head, auto blending, dolby up and down,...) that were only useful for show and tell.  The expensive toys were less likely to have such.. (Conrad-Johnson)
 
For software, "Showroom" features help reviewers know what to comment on. "Oh look, Sonar's new plugin menu divides the "old" from the "newer" and the "newest."
 
This also seems to be a noob feature. Just strikes me as some other S-X series features. Such as the track height minimum is set to make sure a new user will always see the notes gadget. And not being able to scroll the tracks off the track windows so a new user will not call tech support wondering where the tracks went.   
 
Wish I could modify the command-ribbon as easily as fixing the plugin menus.
 
Now there would be a great feature!

Useful for me, it shows me which plugins I should uninstall..