I posted about my experience with Parcel here. Back then you didn’t seem really attracted by the way 
Summary: it’s really fast, just occasionally CPU gets really high or React components get messed up and you have to restart Parcel (which often still takes less time than a Meteor reload). It’s not perfect but it really made a difference. Not just the speed, but the hot reloading (keeping scroll position and component state) is a godsend for productivity, it really helps you stay in the flow. You have to experience it to understand what I mean.