I would agree fully here with Leathermang, not worth scoring the synchros or ruining the throwout bearing on the clutch. I use my clutch for my shifting and my gearboxes have run trouble free and I have had my clutch easily go over 200,000Km.

For motorcycles I would not recommend clutchless shifting either unless one has the air shifter for power shifting during drags. I have seen the great Valentino Rossi upshift clutchless but downshift with clutch but then in case of a genius like Rossi, the who equation is different unlike us mortals.