Wow, that's so much cleaner - why don't they just do it like this in the example? I'd be much happier learning standard web components if they were all a breath of fresh air like this.

Personally I'd miss the JSX syntax, but this more than makes up for it by removing the entire whacky state vs. props thing. Although- how do you represent custom props here - arguments to the constructor? That'd be really elegant.

Do those styles and query selectors leak out of the component? I'm assuming they don't since that's the entire point of the idea of a component, but just want to be sure.