The only reason I can see for upgrading is if you are having problems with the current drivers. I did not have any problems with mine, and like I mentioned I didn't have any problems until I upgraded to the new drivers. I didn't do any real stress testing other than running glxgears and UT. I didn't notice any differences, of course they ran perfectly with the last revision.
I did add a couple of more settings to my XF86Config, like hardware cursor shadowing and Render Accel. I believe those options were available in the last version. The only real reason I installed them was to make sure there were no changes in the installation method in case the original poster needed some more help.