There's some great news today: it's now possible to run the GNOME Shell with Mutter but not having to rely upon any GPU hardware driver! Software rendering is now working with GNOME Shell rather than any fall-back thanks to improvements with Gallium3D's LLVMpipe.
Adam Jackson of Red Hat has announced to the world that it's now possible for everyone to use GNOME Shell, regardless of whether you have a proper 3D hardware driver loaded. Adam says that as of tomorrow, LLVMpipe will no longer be treated as an unsupported driver for Fedora's Rawhide, which is what will eventually be Fedora 17.
rest here