When kicking things off with Doom 3, immediately one can see that even the very latest driver code when put into an ideal state with non-standard configuration options and an out-of-tree Mesa patch, the Radeon Gallium3D driver still cannot compete with Catalyst. Even with the mid-range Radeon HD 4650 and other cards that are years old, the open-source Radeon Linux driver was at a major loss. The Catalyst Linux driver was multiple times faster.
Fortunately, at least, with the "Tweaked Git" configuration there were notable performance gains -- on several of the GPUs -- to find with the id Tech 4 game compared to the default open-source experience in Ubuntu 12.04. Most of these tweaks and Git code will work their way into Ubuntu 12.10 or it may take until Ubuntu 13.04 for 2D color tiling, PCI-E 2.0, etc based upon the current (slow) pace these performance-improving features have been tacked.
The Radeon X1000 series graphics cards were only tested with the open-source drivers since the R300/R400/R500 support in Catalyst was removed back in 2009. There are not open-source results for the Radeon HD 3650 since for both the stock Ubuntu 12.04 and the very latest driver code, the HD 3650 graphics card was too unstable and experienced other issues.