While Warsow is not very GPU-hungry, we ran it anyways with the Radeon HD 4870 and the different Catalyst drivers to see what would come up. Its results were rather interesting with all of the drivers except for the oldest Catalyst 9.1 release. The frame-rate performance with Warsow was dropping rather sharply and strangely with some of the resolution settings and then recovering at other steppings. Catalyst 9.1 exhibited the best performance with this ioquake3 game.
Nexuiz isn't too GPU limited either, but at least we see here the 2009 Catalyst drivers haven't caused any performance regressions in either direction for this very popular open-source game.
With the VDrift racing game there was a performance drop with Catalyst 9.3, but outside of that problem, the performance was stable with the four other tested Catalyst releases from this year.