I can't imagine making hollandaise with melted whole butter.
And when I did pastry, as soon as I started using clarified butter to paint the phyllo dough, my baked blueberry "spring rolls" stopped exploding.
Since I haven't quite got the patience to make ghee, I use clarified butter in Indian recipes. Not quite as authentic, but it still tastes good (well, of course it will; it's BUTTER

)
I wonder, is there any point to trying to make clarified margarine?