I love GNOME and Fedora, but “upgrading” from Fedora 17 to 18 did not go well for me. I recommend you wait until either these are all fixed, or Fedora 19+ suits your needs. Here are a list of problems I had, and some workarounds. Hopefully proper patches to these bugs will get merged quickly, so that you don’t need to use these fixes.
Problem: Boot fails after upgrade from Fedora 17 to Fedora 18. I used the new “fedup” method.
Workaround: I did a fresh install. Make sure you have backups first, of course. I didn’t feel like spending a lot of time debugging why it broke.
<Backspace> key no longer goes “up” in nautilus. I hope this wasn’t a “feature removal”.
(gtk_accel_path "<Actions>/ShellActions/Up" "BackSpace")
to your: ~/.config/nautilus/accels and restart nautilus of course.
Problem: Split view (extra pane) functionality is missing in nautilus 3.6
Workaround: The GNOME developers plan to eventually replace this in a similar form. Until then, you can install the nemo file manager, which is a fork of nautilus 3.4 and is packaged in Fedora 18. (yum install nemo nemo-open-terminal)
Problem: GNOME Shell background is entirely black in overview mode.
Workaround: Using gnome-tweak-tool, under the “Desktop” section, set “Have file manager handle the desktop”, to “OFF”. Unfortunately, this disables viewing of files on your desktop. This wasn’t a problem in Fedora 17.
Problem: Restarting the X server with the familiar Control-Alt-Backspace, can’t be enabled in the keyboard shortcuts menu as it used to.
Workaround: This option is now hidden in the gnome-tweak-tool under typing: terminate.
I hope this scratches your itches!