Another Google Products jumped the Google+ redesin bandwagon -- the latest joine is the Google Groups service that has been redesigned as part of Google's multi-month Google+ inspired user interface update project.
In the refreshed, Google Groups you will find new buttons, new icons, new scrollbars, new search box and a smoother interface that makes Google's help forums look outdated.
Since the current Google Groups UI is inspired by Google Reader, we can expect to see a revamped Google Reader with a similar interface.
If you miss the small arrow that allowed you to hide the sidebar, use the "f" keyboard shortcut, which hides both the sidebar and the search box.
Here are a couple of new Google Groups' screens: (blown up - so looking blured)