Fedora does have a early branching system at the moment and you can use
Fedora 13 branch and it's different from rawhide in the sense that all
updates usually go via an updates-testing repository to the base repository
and Fedora is trying to improve the quality of rawhide itself via some
automated QA tests.
There has been a number of ideas floating around including allowing users
to hook into updates-testing repo and provide feedback more easily. We
will see in the upcoming months some significant changes, I think.