I don't see any mention of how log out works. Is it as soon as the browser window is closed? I'd find that a little annoying on my own device, but it would be essential on a shared computer-- at the library for example.

I'm thinking a checkbox saying "Shared Computer" and issues a link with a different session length (or logout on window close) if checked?

Personally I love this idea as managing passwords has become really unwieldy and I don't trust any password manager service. Plus for a few sites that require really bizarre password length/character requirements/etc., I just reset them overtime I want to log in anyway.