Will you be watching in a dark or bright room? My room is generally pretty dim throughout the day, and I can black it out by shutting the curtains. I'm still within my first few days of having a G series, so my settings are pretty low, but man can the brightness get pretty eye-searing. NHL10, for instance, the demo background on the ps3 menu is exceptionally bright, w/ a mostly white and ice background and the silver stanley cup.
I'm not claiming pure white, or any measured brightness but FWIW if you are in a light controlled room, it's plenty bright.
Infected with the AVS-induced Home Theater Bug.