According to a message on the Fedora mailing list, GNOME Shell should work without 3D acceleration in Fedora 17:
As of tomorrow's rawhide, gnome-session will no longer treat llvmpipe as an unsupported driver. This means gnome-shell will run even on hardware without a native 3D driver, including virt guests.
There are probably bugs! I've done some quick tests on the hardware I have handy and in kvm, and things do appear to work.
That means GNOME Shell will be available for everyone and GNOME Fallback will no longer be required, but this raises a question: will GNOME Fallback still be available (since GNOME Shell will work without 3D acceleration, GNOME Fallback - which exists because until now GNOME Shell didn't run without 3D acceleration -, doesn't have a purpose anymore)?
More info @ https://fedoraproject.org/wiki/Features/Gnome_shell_software_rendering