I'd like to at least have the left sidebar menu open by default, as I use it a lot. Is there a way to not have to click the hamburger menu to open it?
As of 6/1/16, they updated the interface so that the side menu stays open. (Along with other improvements.)
Clicking the hamburger menu icon in the top left (the three stacked vertical lines) toggles visibility of the side menu.
This also works in the new Gmail, Google Calendar, etc as well.
(I do wish Google would make discovering this feature more obvious.)