I really like it.

Mostly the repurposing of the left side for the table of contents, but also the width reduction. I only use half of my screen for my browser already, and on many pages, lines are just insanely long.

Personally, I nevery really minded having open space on websites. I never felt it made reading worse. Contrary, pages with little whitespace felt cramped and I lost my position now and then. But I understand that other people will feel differently about that.

I'd stil like the language selector below the table of contents in the sidebar.