My girlfriend just installed a fresh copy of Ubuntu 12.04.4 64-bit on her PC. After installing and updating the system, Ubuntu has been using the Open Source drivers for her GPU - the AMD HD7850 with 1 GB of GDDR5.
Games such as Nexuiz, Xonotic, Half-Life 1, Starbound and even No More Room in Hell run extremly good, at a minimum of 60fps, 1080p and with high details, but Left for Dead 2 runs at a low framerate (20-30fps) at low details. Other games, such as Rust and Anna, don't run at all (black screen). For this reason, above all, I recommended installing the proprietary AMD video drivers for her GPU.
The question now is; which one is the stable/recommended driver?
They're all the same, they all have the exact same description. I assume one of those is recommended and the others are beta drivers, just like it was in Ubuntu 12.04.3 64-bit. Or maybe the Open Source AMD driver has become the recommended driver, I don't know.