Phoronix reader Dylan Combs wrote in to share the steps he has used to get the Catalyst 14.4 driver successfully working atop Fedora 20 with the updated kernel. However, due to the Catalyst driver conflicting with GNOME 3.10 and its experimental Wayland support, the steps also involve removing the GNOME Desktop Environment and replacing the desktop with KDE.
Besides switching desktop environments, there is an out-of-tree patch that needs to be applied against the fglrx driver's open shim layer so that it will work against the Linux 3.14 kernel. Fedora users dependent upon the Catalyst driver for either OpenGL 4 support, better performance, bugs within the open-source Radeon driver, or features found only within the Catalyst driver, you can find out the Catalyst F20 steps via Dylan's blog.
Dylan has also shared some of his own Catalyst 14.4 Fedora 20 benchmarks showing performance improvements; his benchmarking is done using the Phoronix Test Suite.