Perfectly usable compared to what? A big toolbar at the top, a big toolbar at the bottom, a big sidebar, none of which have any information I want to see; ads

Perfectly usable compared to what? A big toolbar at the top, a big toolbar at the bottom, a big sidebar, none of which have any information I want to see; ads all over, and I have to sign up for their website to download the PDF. That's not even as good as Acrobat (last I used it), never mind a lightweight PDF reader, never mind Chrome's integrated PDF rendering.