Portals seem like a great idea. It seems like it eliminates one of the major use cases (imo) for inlined styles: rendering child components deep within the DOM when visually the component doesn't appear that it should be that deep (e.g., rendering a global level modal that in the DOM might be appear in a deeply nested div). That always wreaked havoc with stylesheet selectors and is one of the reasons I started moving towards injected inline styles.

Overall reduction of container elements is a huge plus. I'll be happy if I can start thinning out the giant christmas tree that react tends to create, even if it's not a huge performance gain, this will improve debugging immensely.