If your graphics card doesn't support 3d-acceleration, Gnome 3 automatically runs the fallback-mode (Kali's Default mode) So instead of the "pretty" Gnome-Shell and Mutter you get the old Metacity and Gnome-panel.
To get your current value,open a terminal and run:
gsettings get org.gnome.desktop.session session-name
To change it run:
dbus-launch gsettings set org.gnome.desktop.session session-name 'gnome'
Then reboot and login.
Took me ages to find this out
