The F15 Gnome 3 live image that was released on May 24 would not
save changes with a persistent overlay so maybe the F15 LXDE spin
was also affected by the no persistence "bug".
What I did was use the "livecd-creator" tool to create a new F15 Gnome 3
spin with the latest updates and with the persistent overlay changes are
saved across reboots. I'm currently creating a F15 LXDE spin and will
see if the persistence works and save changes. Will report back as soon
as the d'load completes and it is installed to usb and tested.