I've tried and tested the modder. It works.
My toshiba satellite A135 series laptop (celeron 1.6Ghz Ati Xpress 200M graphics - bought in 2007) won't accept ATI reference drivers. Install log always indicate failed driver installation. Toshiba proprietary graphics driver can only upgrade upto driver version 8.383.1.1000 (driver date 6/21/2007 :

).
After modding newer reference drivers I was able to upgrade it to driver version 8.561.0.0 (catalyst driver 8.12 - 12/1/2008). I've tried modding catalyst driver 9.3 (3/18/2009) but it doesn't work. Maybe support for the mentioned graphics chip ended.
As for performance, notable smoothness when opening multiple windows. Smoother graphics too when light gaming (Dota, older MMOs).
From the website, It is mentioned that laptop manufacturer support for refence drivers started in 2007. So I guess this modder tool would only help owners with older laptops which rejects ATI reference drivers.