I experimented with the Ultrasonic filter on a just-for-fun master at 96kHz. I had about 10 plugins in a chain (all producing harmonic distortion of various degrees, mainly Acustica Audio Aqua and Nebula instances) and smashed into Voxengo Elephant ridiculously hot (limiting up to 8dB at best). I inserted Ultrasonic filter first in the chain and then after (and thus before) each and every plugin, including after elephant (so actually after the limiting.. just before final dither). The difference is ASTONISHING!! It is so ridiculously obvious and much better with the filters than without. A truly mind-blowing "WTF???!!" experience for me. It basically removed a lot of problems I've identified in mixes and previous masters that had heavy processing with a lot of harmonics.. mainly that nasty build up of "ringing" around 2.3 to 4kHz area. It also cleared out the congested mids and lower mids. This is a game changer for me. I will not do any more high resolution mastering without this filtering. Period. Heck, I will never mix at high resolution again without this plugin inserted all over the place.