It seemed to start with 7.5.20.
But I recently upgraded my hardware.
Today I found, that the preset window loads slow on all my 3 main screens
( attached to an ATI 6850 with newest drivers ).
It opens instantly on my 4th display, connected to the on chip Intel GPU …
Aero is on.
Does it use open GL ?? Probably not, as Waves GUIs work flawless, since activating Aero.