For me, the sidebar is a big positive step.
One consistent complaint we had with users who were not too tech savvy was that the discourse interface was hard to fathom. While there was so much functionality, users did not know what to do after landing on the home page. The sidebar is something we have been looking for, is practical and so much in the face for users to click and explore. It exposes several functions that should be regularly tracked but are normally tucked away.
The new hamburger behavior however seems non standard - hiding the sidebar on click when one would normally expect it to open a drop down menu.