A word of warning, I just tried to downgrade via ppa-purge from xorg-edgers and it did not go well. In 12.04 and prior I could do that happily by running ppa-purge and re-installing the various packages it tried to remove since it doesn't play well with multi-arch. However it lefts a large number of packages on the system from xorg-edgers without downgrading them. So I would not suggest using it to test unless you want to do some serious packge surgery after.
A word of warning, I just tried to downgrade via ppa-purge from xorg-edgers and it did not go well. In 12.04 and prior I could do that happily by running ppa-purge and re-installing the various packages it tried to remove since it doesn't play well with multi-arch. However it lefts a large number of packages on the system from xorg-edgers without downgrading them. So I would not suggest using it to test unless you want to do some serious packge surgery after.