With GNOME Shell 2.91.90, there are workspace handling changes, a PolicyKit authentication agent, visual refreshments, suspend support is now shown from the power-off menu while the power-off button is concealed by default (hold down Alt to see), message tray improvements, Shell Toolkit improvements, memory leak fixes, Telepathy support being ported to a telepathy-glib library, and other work. The visual refresh is improving the appearance and behavior of the overview dash, using larger icons in the application browser, improving the top panel and round corners of the screen, and improving the search entity in the overview. Read more in the release announcement.
The Mutter 2.91.90 release carries various fixes and it can be read about in its release announcement.
The GNOME 3.0 Beta is expected to be released today while a second beta is coming in early March, a release candidate near the end of March, and the official GNOME 3.0 release on the 6th of April.