The main draw back, that nobody seem to think about is that fact that when you flat a tubular tire, you can still ride it at a fast pace to the pit to switch bikes. Anybody you has flatted with clinchers knows that when you flat you dont have the same control. And when you add in sealant to tubeless tires, it acts as a lubricant and it makes the slipping of the tire on the rim 10X worse. Tubeless for training? Yes, Tubeless for racing? a decent alternative, but still not the same advantage as tubulars.