Might also depend on how you use it. I have no repositories which I maintain on github worth speaking of, I only contribute, so 99% of time I spend in issue/PR views to which I go directly via links from notification emails.
While as pointed out above the decision of making the top navigation bar span the screen is rather unfortunate, the main thing I see is that instead of the smartphone-centered (or whatever reason) design the central part where the comments are shown is now like 50% wider. Which is something I always wanted because I only use this on desktop and usually with the browser full-screen so finally it takes some advantage of the available space.
However the width used also depends on whether the sidebar is there or not which is quite jarring. I.e. in the toplevel file tree view there's a sidebar. But when you then click on a directory the sidebar is gone and the witdh taken by the tree view expands. That's not ideal and just jarring when going back and forth. So for cases like that, it's not merely the fact there was a change which causes friction, it's really the new version which does.
While as pointed out above the decision of making the top navigation bar span the screen is rather unfortunate, the main thing I see is that instead of the smartphone-centered (or whatever reason) design the central part where the comments are shown is now like 50% wider. Which is something I always wanted because I only use this on desktop and usually with the browser full-screen so finally it takes some advantage of the available space.
However the width used also depends on whether the sidebar is there or not which is quite jarring. I.e. in the toplevel file tree view there's a sidebar. But when you then click on a directory the sidebar is gone and the witdh taken by the tree view expands. That's not ideal and just jarring when going back and forth. So for cases like that, it's not merely the fact there was a change which causes friction, it's really the new version which does.