Well, with this code now hitting Mesa's master code-base, it will become part of Mesa 7.6 and should be picked up soon in time for the next round of Linux distribution updates. Pulling in the radeon-rewrite branch had led to the deletion of 18,854 lines of code and the addition of 16,432 lines of new code. Beyond the improvements that the rewritten driver immediately brings, the open-source 3D support for the ATI R600/700 series is being worked on as a branch of the radeon-rewrite driver, therefore it was a prerequisite that this code first be merged into Mesa.
This radeon-rewrite merger is also good news for those interested in the forthcoming merger of the TTM memory manager and Radeon kernel mode-setting into the Linux 2.6.31 kernel.
The mailing list announcement of the Radeon Rewrite going mainline can be found at SourceForge.