Some of us have had a more nuanced experience with Class D than TEO_Audio.... I have been listening to class D since 2006.... I have heard class D purgatory, hell, and class D heaven since then. Have been experiencing musical nirvana in my own system with class D amps since 2008.
I have also experienced for several days one quite promising GaN-based prototype amp in my system, which, because it was incomplete nd not well broken in, was still displaying some minor audible artifacts in the treble region... Yet, was in spite of this, as I said... Very promising.
So, my ever cautious inclination is to say that GaN may be, if not the only way to create excellence with class D, at least one of the emerging technologies with high potential.
As more GaN amps are released in the next few years, we might have a better idea if the potential for generating nirvana is inherent to GaN transistors, or if GaN technology per se has instead an average chance to be inside superior amps.
Guido